Amino AcidsAmino Acids

- Dietary proteins are the primary source of a.a.s for

endogenous protein synthesis.

- a.a.s in blood are filtered through the glomerular membranes

then reabsorbed in the renal tubules by saturable transport

systems. When the transport mechanism becomes saturated or

is defective, a.a.s spill into the urine resulting in

aminoaciduria.

Two types of aminoaciduria have been identified:

1. 1. Overflow aminoaciduriaOverflow aminoaciduria: which occurs when the plasma

level of one or more a.a.s exceeds that of renal threshold

(tubular capacity for reabsorption).

2. Renal aminoaciduria:2. Renal aminoaciduria: which occurs when plasma levels

are normal but the renal transport system has a congenital or

acquired defect.

The aminoaciduria

- Aminoaciduria may be primary or secondary.

Primary disease: due to an inherited enzyme

defect, also called inborn error of metabolism.

-The defect is located either in the pathway by which a

specific a.a. is metabolized or in the specific renal

tubular transport system by which the a.a. is

reabsorbed.

-The defect in the enzyme results in substrate

accumulation or its diversion into alternative paths.

Products of the normal path are not formed at all or

formed in smaller amounts.

Secondary aminoaciduria:

- Secondary aminoaciduria: could be due to either to

disease of an organ such as the liver, which is an active

site of a.a. metabolism, or a generalized renal tubular

dysfunction.

- It can affect many a.a. simultaneously

Examples of disorders that result in secondary overflow

amnioaciduria are acute viral hepatitis and

acetaminophen poisoning.

Generalized secondary renal aminoaciduriaGeneralized secondary renal aminoaciduria is due

to progressive damage to the renal tubules

It can be caused by poisons (especially heavy metal), or

disease, or by congenital conditions such as Wilson’s

disease.

Amino acid disorders

• Phenylketonuria (PKU)

• Urea cycle disorders

• Tyrosinaemia type 1

• Homocystinuria

• Maple syrup urine disease (MSUD)

• Renal transport disorders

– Cystinuria

Amino acid disorders

Selected disorders of a.a. metabolismHyperphenylalaninemias: these are a group of disorders resulting from impaired conversion of phenylalanine to tyrosine due to the defect in phenyalanine hydroxylase that found only in the liver and kidneys.

Defects in this enzyme Hyperphenylalaninemia phenylalanine accumulates in blood, urine and CSF phenylketonuria (PKU)

Untreated PKU results in severe mental retardation.

* Affected children appear normal at birth, and the earliest symptoms are usually nonspecific-delayed development, feeding difficulties and vomiting.

* Children with PKU elicit an unusual but characteristic musty odor in urine or sweat, owing to increased production of phenylpyruvate.

* Early diagnosis is essential to avoid the adverse effects of PKU and consequently neonatal screening has become widespread.

Phenylketonuria (PKU)Phenylketonuria (PKU)

Elevated blood-phenylalanine activates the normal minor metabolic pathways of phenylalanine increased production of phenylketones (e.g., phenylpyruvate) and other metabolites that excreted into the urine.

Treatment of PKU consists of restricting dietary phenyalanine before the onset of brain damage

TyrosinemiaTyrosinemia

* Tyrosinemia has several forms, each of which is accompanied by high level of tyrosine and phenolic aciduria.

* Tyrosine is essential for protein synthesis and serves as a precursor for thyroxine, melanin and catecholamines.

* The pigment melanin is derived from tyrosine by the activity of tyrosinase.

* Clinical syndromes resulting from inherited defects in melanin synthesis are collectively known as albinism.

Albinism refers to a group of conditions in which a defect in tyrosine metabolism results in a deficiency in the production of melanin.

These defects result in the partial or full absence of pigment from the skin, hair, and eyes.

Albinism appears in different forms, and it may be inherited by one of several modes.

Complete albinism (also called tyrosinase-negative oculocutaneous albinism) results from a deficiency of tyrosinase activity, causing a total absence of pigment from the hair, eyes, and skin

It is the most severe form of the condition.

AlbinismAlbinism

Cystinuria:

Classic cystinuria is the most frequently inborn error of a.a.

transport. This disease is characterized by massive excretion of

cystine, lysine, arginine and ornithine.

Normally these a.a.s are filtered by the glomerulus and

reabsorbed in the proximal renal tubule.

In cystinuria re-absorption fails because a carrier system that

transports all a.a.s is defective.

Because cystine is the least soluble of all the naturally

occurring a.a.s, its overexertion often leads to the formation of

cystine caliculi in the renal pelvis, ureters, and bladder;

obstruction, infection, and renal insufficiency occasionally result.

Treatment involves reducing the concentration of cystine in

urine by drinking large amounts of water, increasing cystine

solubility by maintaining the urine alkaline and, if necessary,

reducing cystine excretion by using pencillamine

Maple syrup urine disease:

Maple syrup urine disease (MSUD) takes its name from the

characteristic maple syrup or burnt sugar odour of the urine of

affected persons which is due to high concentrations of aliphatic

keto acids.

a.a. analysis of blood and urine show high levels of leucine,

isoleucine and valine.

These branched-chain a.a.s are normally converted by

transamination to their corresponding -keto acids, by the enzyme

branched-chain amino transfersae then oxidized into acyl-

coenzyme A (CoA) derivatives by branched-chain -keto acid

dehydroghenase

An inherited defect in the enzyme branched-chain -keto acid

dehydroghenase results in accumulation of the branched-chain

a.a.s and their corresponding -keto acids in blood, urine and CSF.

Maple syrup urine disease:

Amino acid disorders

PLASMA ENZYMES

- Measurements of the activity of enzymes in plasma are of value in the diagnosis and management of a wide variety of

diseases.

- Most enzymes measured in plasma are primarily intracellular, being released into the blood when there is damage to cell

membranes,

-Small amounts of intracellular enzymes are present in the blood as a result of normal cell turnover.

- When damage to cells occurs, increased amounts of enzymes will be released and their concentrations in the blood will rise.

- However, such increases are not always due to tissue damage.

- Other possible causes include: increased cell turnover, cellular proliferation (e.g. neoplasia), increased enzyme synthesis (enzyme

induction), obstruction to secretion, decreased clearance.

- Many other enzymes, for example renin, complement factors and coagulation factors, are actively secreted into the blood, where they

fulfill their physiological function.

A major disadvantage in the use of enzymes for the diagnosis of

tissue damage is their lack of specificity to a particular tissue or

cell type.

Many of these enzyme are not used as diagnostic tool but used

for monitoring the diseases

Many enzymes are common to more than one tissue

This problem may be overcome to some extent in two ways:

A) First, different tissues may contain (and thus release when they are

damaged) two or more enzymes in different proportions; e.g. alanine and

aspartate aminotransferase are both present in cardiac muscle and

hepatocytes, but there is relatively more alanine transaminase in the

liver;

B) Second, some enzymes exist in different forms (isoforms), termed

isoenzymes.

Individual isoforms are often characteristic of a particular tissue.

So the pattern of increase of different enzymes can indicate the site of

problem, e.g. high GGT and high ALP or AST indicates a problem in the

liver

While high ALT and CK-MB indicates MI

Factors Affecting Results of Plasma Enzyme Assays

Analytical factors affecting results.

Results of enzyme assays are not usually expressed as concentrations, but as activities.

So the results of such measurements depend on many analytical factors including the concentrations of the substrate and product, the pH and temperature at which the reaction is carried out, the type of buffer, and the presence of activators or inhibitors.

Physiological factors affecting enzyme activities, include for example:

age: plasma aspartate transaminase activity is moderately higher during the neonatal period than in adults;

plasma alkaline phosphatase activity of bony origin is higher in children than in adults.

sex: plasma gama-glutamyltransferase activity is higher in men than in women

physiological conditions: plasma alkaline phosphatase activity rises during the last trimester d pregnancy because of the presence of the placental isoenzyme;

several enzymes, such as the transaminases and creatine kinase, rise moderately in plasma during and immediately after labour or strenuous exercise.

Two important transferases:

Alanine aminotransferas (ALT) called

also Glutamate – Pyruvate transferase

(GPT) or Serum ALT = SGPT, found in

many tissues catalyzes the transfer of

amino gp of alanine to produce pyruvate

and glutamate.

Aspartate aminotransferase (AST)

called also Glutamate–Oxaloacetate

transferase (GOT) or Serum AST = SGOT,

- During the catabolism of amino acids AST

takes amino group from glutamate to

oxaloacetate forming aspartate. Which

used as source of NH4 group in Urea

synthesis

Aspartate source of amino group of the

urea in the urea cycle.

Aspartate Transaminase (AST): 10-45 U/L

AST (glutamate oxaloacetate transaminase GOT) is present in high

concentrations in cells of cardiac and skeletal muscle, liver,

kidney and erythrocytes.

Damage to any of these tissues may increase plasma AST levels.

AST can be used as indicator of muscle damage.

Causes of Raised Plasma AST Activities

* Artifact: due to in-vitro release from erythrocytes if there is

haemolysis or if separation of plasma from cells is delayed.

*Physiological: during the neonatal period (about 1.5 times the

upper adult reference limit).

*Marked increase (10 to 100 times the upper adult reference limit):

circulatory failure with 'shock' and hypoxia; myocardial infarction;

acute viral or toxic hepatitis.

Aspartate Transaminase (AST)

*Moderate increase:

Cirrhosis (may be normal, but may rise to twice the upper adult

reference limit); infectious mononucleosis (due to liver

involvement (type of viral infection “mononucleosis” refers to

an increase in a special type of white blood cells (lymphocytes);

cholestatic jaundice (up to 10 times the upper adult reference

limit); malignant infiltration of the liver; skeletal muscle

disease; after trauma or surgery (especially after cardiac

surgery); severe hemolytic episodes (of erythrocyte origin).

Alanin Transaminase (ALT): 10-50 U/L

ALT (glutamate pyruvate transaminase, GPT) is present in high concentrations in liver and, to a lesser extent, in skeletal muscle, kidney and heart

ALT is more specific for liver than muscle

Causes of Raised Plasma ALT Activities

*Marked increase (10 to 100 times the upper limit of normal (ULN)):

- acute viral or toxic hepatitis.

- circulatory failure with 'shock' and hypoxia;

*Moderate increase:

-cirrhosis (may be normal or up to twice*ULN);

-infectious mononucleosis (due to liver involvement);

-liver congestion secondary to congestive cardiac failure;

-cholestatic jaundice (up to 10 times the upper reference limit in adults);

-surgery or extensive trauma and skeletal muscle disease (much less affected than AST).

Gamma-glutamyl-transferase (GGT)

GGT occurs mainly in the cells of liver, kidneys, pancreas and prostate.

Plasma GGT activity is higher men <50 U/L) than in women <30 U/L.

It is very sensitive but unspecific indicator for liver dysfunction;

Sensitive anything wrong in the liver will elevate its activity but non-specific can’t indicate the reason of liver disease

Causes of raised plasma GGT activity

-Induction of enzyme synthesis, without cell damage, by drugs or alcohol. Many drugs most commonly the anticonvulsant phenobarbitone and phenytoin, and alcohol induce proliferation of the endoplasmic reticulum.

- Cholestatic liver disease, (cholestasis is a condition where bile cannot flow from the liver to the duodenum): changes in GGT activity usually parallel those of alkaline phosphatase.

-In biliary obstruction, plasma GGT activity may increase before that of alkaline phosphatase.

- Hepatocellular damage, such as that due to infectious hepatitis; measurement a plasma transaminase activities is a more sensitive indicator of such conditions.

- Plasma GGT activity is frequently very high in patients with alcoholic liver disease and can be elevated, due to enzyme induction, the absence of of liver damage

Alkaline Phosphatase (ALP)

-The alkaline phosphatases are a group of enzymes that

hydrolyze organic phosphates at high pH.

-They are present in most tissues but are in particularly high

concentration in the osteoblasts of bone and the cells of

the hepatobiliary tract, intestinal wall, renal tubules and

placenta.

-The exact metabolic function of ALP is unknown but it is

probably important for calcification of bone.

- In adults plasma ALP is derived mainly from bone and

liver in approximately equal proportions; the proportion

due to the bone fraction is increased when there is

increased osteoblastic activity that may be

physiological.

Causes of raised plasma ALP activity

Physiological:

during the last trimester of pregnancy the plasma total ALP activity rises due

to the contribution of the placental isoenzyme

Bone disease:

Rickets and osteomalacia;

Rickets: is an abnormal bone formation in children resulting from

inadequate calcium in their bones

Osteomalacia: softening of the bones, resulting from defective bone

mineralization in adults

Paget's disease and (ALP may be very high); Paget's disease is a chronic

bone disorder that is due to irregular breakdown and formation of bone

tissue.

Primary hyperparathyroidism with extensive bone disease

Liver disease:

intra- or extrahepatic cholestasis, lesions, tumor, granulomas, and other

causes of hepatic infiltration.

Malignancy: bone or liver involvement or direct tumor production.

Homolactic fermentation: conversion of pyruvate to lactate

Lactate dehydrogenase

Reduction of pyruvate to lactate

- Lactate is formed by the action of

Lactate dehydrogenase

- It is the final product of anaerobic

glycolysis in eukaryotic cells

- It is also formed in RBC, lens and

cornea of the eye, kidney medulla,

testes and leukocytes

Lactate Dehydrogenase (LD): 110-230 U/L

- The enzyme is widely distributed in the body, with high

concentrations in cells of cardiac and skeletal muscle, liver,

kidney, brain and erythrocytes;

- Measurement of plasma total LD activity is therefore a nonspecific

marker of cell damage.

-Causes of Raised Plasma Total LD Activity.

Artifact:

- due to in vitro haemolysis or delayed separation of plasma from

whole blood.

Marked increase (more than 5 times ULN):

-Circulatory failure with 'shock' and hypoxia;

- Myocardial infarction

-Some hematological disordersas megaloblastic anaemia, acute

leukaemias and lymphomas,

Creatine Kinase (CK)

CK is most abundant in cells of cardiac and skeletal muscle and

in brain, but also occurs in other tissues such as smooth muscle.

Causes of raised plasma CK activities

*Artifact: due to in vitro haemolysis

*Physiological: neonatal period (slightly raised above the adult

reference range).

Marked increase:

Circulatory failure and shock; myocardial infarction;

Muscular dystrophies and high breakdown of skeletal muscle.

The muscular dystrophies are the most-known group of hereditary

muscle diseases; characterized by progressive skeletal muscle

weakness, defects in muscle proteins, and the death of muscle cells

and tissue.

Creatine Kinase (CK)

Moderate increase:

Muscle injury; after surgery (for about a week); physical effort, moderate exercise and muscle cramp;

an intramuscular injection; hypothyroidism (thyroxine may influence the catabolism of the enzyme); alcoholism (due to alcoholic myositis (inflammation of the muscle)ISOENZYMES OF CK

CK has 3 isoenzymes:

CK-MM (CK-3) is the predominant isoenzyme in skeletal and cardiac

muscle and is detectable in the plasma of normal subjects.

CK-MB (CK-2) accounts for about 35 % the total CK activity in cardiac

muscle and less than 5% in skeletal muscle;

Its plasma activity is always high after myocardial infarction.

CK-BB (CK-1) is present in high concentrations in the brain and in the

smooth muscle of the gastrointestinal and genital tracts.

Raised plasma activities may occur during labour and child birth.

Non-specific Causes of Raised Plasma Enzyme Activities

Change in plasma enzyme activity could be due to nonspecific

causes

-Slight rises in plasma aspartate transaminase activities

are common in non-specific findings in many illnesses.

- Moderate exercise, or a large intramuscular injection,

may lead to a rise in plasma creatine kinase activity;

- Some drugs, such as the anticonvulsants phenytoin and

phenobarbitone, may induce synthesis of the microsomal

enzyme, gammaglutamyltransferase, and so increase its

plasma activity in the absence of disease.

- Plasma enzyme activities may be raised if the rate of

clearance from the circulation is reduced.

Plasma Proteins

Proteins: are polymers of a.a.s that are covalently linked through peptide bonds.

The different R groups found in a.a.s influence the structure, functionality and properties of the individual proteins.

Proteins may be classified as fibrous (mainly structural) or globular.

*Nearly all other proteins of clinical interest are soluble globular proteins such as haemoglobin, enzymes and plasma proteins.

*The complex bending and folding of polypeptide chains is a result of numerous interactions of their R groups.

*Globular proteins are compact and have little or no space of water in the interior of the molecule, where most of the hydrophobic R groups are located.

*Most polar R groups are located on the surface of the protein where influence on protein solubility, acid-base behaviour and electrophoretic mobility

*Most globular proteins are affected with temperature and pH.

Functions of plasma proteins

Function Example

Transport

Immunity

Maintenance of oncotic pressure

Enzymes

Protease inhibitors

Buffering

Thyroxine-binding globulin

(thyroid hormones)

Apolipoproteins (cholesterol,

triglycerides)

Transferrin (iron)

Immunoglobulins

All proteins, particularly albumin

Renin

Clotting factors

Complement proteins

1-antitrypsin (acts on proteases)

All proteins

Plasma proteins

- Over 100 individual proteins have a physiological function in the plasma. Quantitatively, the single most important protein is albumin. The other proteins are known collectively as globulins.

Protein Properties

- Many of the properties of proteins are used for their separation, identification and assay:

1-Molecular size: Most proteins are macromolecules, so can be separated from smaller molecules by dialysis or ultrafiltration, chromatography and by density-gradient ultracentrifugation

2. Differential solubility: Protein solubility is affected by the pH, ionic strength, temperature and dielectric constant of the solvent.

3. Electrical charge: Separation by electrophoresis, this is based on the capability of a mixture of proteins with various species of different charge/mass ratios to migrate at different rates in an electrical field.

4. Adsorption on finely divided inert materials: These materials offer a large surface area for interaction with protein, such as charcoal,

silica or alumina.

5. Specific binding to antibodies, coenzymes, or hormone receptors: The unique properties of protein to recognize and bind to a

complementary compound with high specificity is the basis for immunoassays.

Analysis of proteins

Methods for the analysis of proteins in body fluids can be grouped as follows:

1. Quantitative measurements of total protein and albumin.

2. Separation by electrophoresis, which provides semiquantitative estimations of the main classes of proteins present in fairly high concentrations.

3. Specific quantitative assays of particular proteins by immunoassays using specific antisera and measurement of antigen-antibody complexes.

4. Detection and identification of abnormal proteins.

Serum Protein Electrophoresis

*Electrophoresis separates proteins according to their different electrical charges

*It is usually performed by applying a small amount of serum to a strip of cellulose acetate or agarose and passing a current across it for standard time.

Serum Protein Electrophoresis

Electrophoresis separates proteins into five main groups of proteins, albumin and the 1-,2-,- and -globulins,

Anode

Cathode

Anode Cathode

Principal bands seen after electrophoresis on cellulose

acetate of normal adult serum

1. Albumin, usually a single protein, makes up the most obvious

band.

2. 1-Globulins consists almost entirely of 1-antitrypsin.

3. 2-Globulins consists mainly of 2-macro-globulin and

haptoglobin.

4. -Globulins often separate into two; 1 consists mainly of

transferrin with a contribution from LDL and 2 consists of C3

complement.

5. -Globulins are immunoglobulins. Some immunoglobulins are

found also in the 2 and regions.

- If plasma rather than serum is used, fibrinogen appears as a distinct

band in the - region. This may make interpretation difficult; blood

should be allowed to clot and serum used if electrophoresis is to be

performed.

Principal plasma proteinsClass Protein Approximate mean serum

concentration (g/L)

prealbumin 0.25

albumin albumin 40

1-globulin 1-antitrypsin

1-acid glycoprotein

2.91.0

2-globulin haptoglobins2-macroglobulin

caeruloplasmin

2.02.60.35

-globulin transferrinlow density lipoprotein

complement components (C3)

3.01.01.0

-globulins IgGIgAIgMIgDIgE

14.03.51.50.03trace

Many other important proteins are present in only very low concentration

Serum protein electrophoresis: applied to the serum not plasma

*Electrophoresis separates proteins into five main groups of

proteins, albumin and the 1-,2-,- and -globulins, may be

distinguished after staining and may be visually compared with those in a normal control serum.

*Each of the globulin fractions contain several proteins.

*Changes in electrophoretic patterns are most obvious when:

1. The concentrations of protein, such as albumin, which is usually in high concentration, are abnormal.

2. There are parallel changes in several proteins in the same fraction.

3. New band that is not seen in normal serum.

Electrophoretic patterns in disease:

Some abnormal electrophoretic patterns are characteristic of a particular disorder or while others indicate non-specific pathological

processes.

For example, the 2 band which contains haptoglobin may be reduced if

there is in vivo haemolysis and split into two if in vitro haemolysis has occurred.

Parallel changes in all fractions. Reduction may occur in sever malnutrition, unless accompanied by infection or haemodilution.

The acute-phase pattern. Tissue damage of any kind triggers the sequence of biochemical and cellular events associated with inflammation.

The biochemical changes include stimulation of synthesis of the so-called

acute-phase proteins, with a rise in the 1- and 2-globulin fractions

increase the erythrocyte sedimentation rate (ESR).

Chronic inflammatory state: usual increase in immunoglobulin synthesis may be visible as a diffuse rise in -globulin.

Nephrotic syndrome. Plasma protein changes depend on the severity of the renal lesion.

Plasma proteins

- Proteins are present in all body fluids including blood plasma. These proteins are examined frequently for diagnostic purposes.

- The amount of protein in the vascular compartment depends on the balance among:

1. The rate of synthesis

2. The rate of catabolism or loss

3. The relative distribution between the intra- and extravascular

compartments the concentration depends on the relative amounts

of protein and water in the vascular compartment.

- Many plasma proteins are synthesized in the liver. Some proteins are synthesized both in cells and macrophages. Immunoglobulins are mainly derived from the B cells of the immune system.

- Most plasma proteins are taken up by pinocytosis into the capillary endothelial cells or mononuclear phagocytes where they are catabolized. Some are catabolized by renal tubular cells.

- Small proteins are lost passively through the renal glomeruli and intestinal wall. Some are reabsorbed, either directly by renal tubular cells or after digestion in the intestinal lumen

Total plasma protein (62-80 gm/L)

- Alterations in plasma protein can be due to

A) Change in the concentration of a specific protein in plasma (due to changes in the rate of synthesis or removal)

B) Change in the volume of distribution (plasma water).

*Decrease in the volume of plasma water (haemoconcentration) as relative hyperproteinaemia concentrations of all plasma proteins are

increased to the same degree

*Hyperproteinaemia is caused by:

1) dehydration (haemoconcentration) due to inadequate water intake or excessive water loss, as in sever vomiting, diarrhoea, diabetic acidosis.

2) an increase in the concentration of specific protein normally present in relatively low concentration, as, for example, increases in APRs and polyclonal or monoclonal immunoglobulins as a result of infection.

* Hypoproteinaemia: caused by a) decreased synthesis, b) Haemodilution and c) protein redistribution.

Haemodilution (increase in plasma water volume) hypoproteinaemia; concentrations of all the individual plasma proteins are decreased to the

same degree. Haemodilution occurs with water intoxication or salt retention syndromes, during massive intravenous infusions.

Total plasma protein

*A rapid decrease in protein concentration is most frequently due to

1) An increase in plasma volume.

2) Capillary permeability increases in patients with septicaemia or generalised inflammatory conditions since proteins will diffuse out into

the interstitial space.

* The concentration of plasma proteins is affected by posture

* Albumin is present in such high concentrations that low levels of this

protein alone may cause hypoproteinaemia

*Plasma total protein concentrations may be misleading: They may be

normal in the presence of quite marked changes in the constituent

proteins.

a fall in plasma albumin concentration may be balanced by

a rise in immunoglobulin concentrations, it is quite common.

Most individual proteins except albumin contribute little to

the total protein concentration; quite a large percentage

change in the concentration of one may not cause a detectable

change in the total protein concentration.

Plasma protein can be divided into

1) Acute phase reactants (APR) these proteins have specific role in inflammatory response so they will increase in inflammatory conditions

2) Negative acute phase reactants these proteins have no role in in inflammation but number of these proteins decrease in inflammatory conditions.

Like albumin, prealbumin, transferrin ….

Specific plasma proteinsSpecific plasma proteins

Albumin (35-47 gm/L)Albumin (35-47 gm/L)

* The most abundant plasma protein representing 40-60% of the

total protein.

* It is synthesised in the liver at a rate that is dependent on protein

intake but subject to feedback regulation by the plasma albumin

level.

* Contributes largely to the oncotic pressure of plasma. Oncotic

pressure is the osmotic pressure due to the presence of proteins

and is an important determinant of the distribution of

extracellular fluid (ECF) between the intravascular and

extravascular compartments.

* The chief biological functions of albumin are to:

• Transport and store wide variety of ligands.

• Maintain the plasma oncotic pressure.

• Serve as a source of endogenous a.a.s.

Hypoalbuminaemia

* Low albumin concentration may be due to dilution or redistribution.

* True albumin deficiency may be caused by a decreased rate of synthesis, or by an increased rate of catabolism or loss from the body.

Causes of hypoalbuminaemia

Decreased synthesisMalnutrition: resulting in an inadequate supply of dietary nitrogenMalabsorption: resulting in impaired absorption of dietary peptides and a.a.Liver diseaseIncreased volume of distributionOverhydrationIncreased capillary permeability: septicaemiaIncreased excretion/degradationNephrotic syndromeBurnsHaemorrhageCatabolic states: severe sepsis, fever, trauma, Malignant disease

Consequences of hypoalbuminaemia

1. Fluid distribution.

The decreased plasma oncotic pressure disturbs the equilibrium between

plasma and interstitial fluid there will be a decrease in the movement of

the interstitial fluids back into the blood accumulation of interstitial fluid

(edema) relative decrease in plasma volume fall in renal blood flow

stimulates the secretion of renin, and aldosterone through the formation

of angiotensin sodium retention and thus an increase in ECF volume

which potentiates the edema.

2. Binding functions.

Albumin is a high capacity, low affinity transport protein for many

substances, such as thyroid hormones, calcium, bilirubin and fatty acids.

Many drugs are bound to albumin in the blood stream as salicylates,

penicillin and sulphonamides.

The drug fraction that is bound to albumin is physiologically and

pharmacologically inactive A reduction in plasma albumin, may increase

the plasma free concentration of those drugs cause toxic effects

HyperalbuminaemiaHyperalbuminaemia

Hyperalbuminaemia may be due to :

An artefact, a result of venous stasis during blood collection (a sample

that was taken from an arm at an excessively long cuffing period)

Over-infusion of albumin

Dehydration: high level of plasma albumin-greater than 50 g/l is usually

indicative of severe dehydration.

Albumin synthesis is increased in some pathological states but never

causes hyperalbuminaemia.

- The plasma albumin concentration is used as a test of liver

function. Because of its relatively long half-life (approximately 20 days) in

the plasma,

- Albumin concentration is usually normal in acute hepatitis.

- Albumin test is not useful marker for short term acute function of

the liver

- Low Albumin concentrations are characteristic of chronic liver

disease, due to both decreased synthesis and an increase in the volume of

distribution as a result of fluid retention and the formation of ascites (free

fluid in the peritoneal cavity).

2-Macroglobulin (α2M)

- The largest plasma protein.

- 2-Macroglobulin inhibits proteases that released in inflammatory

conditions and destroy the tissues and cells its main function to

protect tissues from proteases and it is not released during acute

inflammation.

- It is not APR.

- Because of its large size, it tends to remain in the intravascular

compartment.

- It is synthesised in the liver and in the reticuloendothelial system.

- It increases in nephrotic syndrome, because it is retained and will

not be lost because of its large size.

- Its hepatic synthesis increases in order to compensate partially for

the decrease in albumin normally active in maintaining the oncotic

pressure.

Transferrin (TRF) : B-globulin protein (2.1-3.6 g/L)

* It is synthesized mainly in the liver, and in the endocrine glands as

ovaries and tests.

* TRF is a -globulin which is the major iron-transporting protein in

the plasma.

* It reversibly binds numerous cations iron, copper, zinc, cobalt and

calcium-although only iron binding appear to have physiological

significance.

* TRF is normally about 30-40% saturated with iron and its half life 7

days.

* Its concentration correlates with the total iron-binding capacity of

serum.

Measurements of plasma transferrin level is useful for the

differential diagnosis of anaemia and for monitoring its

treatment.

Transferrin (TRF) : (2.1-3.6 g/L)

*TRF Plasma levels are regulated by availability of iron iron

deficiency, TRF rise and, upon successful treatment with iron, it

returns to normal level.

* In common iron deficiency, the TRF level is increased due to

increases in synthesis this guarantee that any amount of iron

absorbed will be transported and bound to TRF directly and in this

case the % of saturation will be less than 30% the protein is less

saturated with iron because plasma iron levels are low

*If the anemia is due to failure to incorporate iron into erythrocytes,

Vit B12 or folic acid deficiency the TFR level is normal or low but the

protein is highly saturated with iron.

High levels of TRF occur in pregnancy and oestrogen administration.

1-Fetoprotein (AFP)

- It is the principal foetal protein.

- Appears in infantile urine it presents in amniotic fluid and maternal blood

- It is determined in amniotic fluid and in maternal serum for the antenatal diagnosis (tests before the birth) of neural tube defects.

- Neural tube defect (NTD): A major birth defect caused by abnormal development of the neural tube, the structure present during embryonic life which

gives rise to the central nervous system ‘the brain and spinal cord”. Neural tube defects (NTDs) are among the most common birth defects that cause infant mortality

(death) and serious disability. There are a number of different types of NTDs

During the foetus growth the CNS starts with the spinal cord then the nervous

system 1-Fetoprotein test is done in the 4th months of pregnancy to make

sure that CNS of the foetus is developing normally. High level of this protein due the leakage to the amniotic fluid and to mother serum indicates defect

in CNS development

- Detection of higher AFP than the normal in early pregnancy can suggest CNS defects

* Gross elevations of AFP serum levels are found in approximately 80% of patients with hepatocellular carcinoma,

* Sequential assays are particularly useful for prognosis and for monitoring treatment.

Anencephaly: congenital absence of all or a major part of the brain

Spina bifida

Neural tube defect (NTD):

Acute phase reactants (APR)

Are protein synthesized in the liver in response to inflammatory

mediators cause the non-specific changes in plasma protein

concentrations, in response to acute or chronic tissue damage and other

inflammatory responses

The acute-phase reactants include:

1) Activators of other inflammatory pathways such as C-reactive

protein, so called because it reacts with the C-polysaccharide of

bacteria. During this response, the concentrations of C-reactive protein

may increase as much as thirty-fold.

2) Inhibitors for enzymes released in inflammation such as 1-

antitrypsin, so they will protect body cells from the attack from these

enzymes.

3) Scavengers such as haptoglobin which binds haemoglobin

released by local in vivo haemolysis during the inflammatory response.

C-reactive protein

- It is a substance in the sera of acutely ill patients.

- It binds and complexes with the polysaccharides present in many

bacteria, fungi and protozoal parasites and becomes an activator of the

classic complement pathway.

* C-reactive protein, dramatically increases following myocardial

infarction, trauma, infections, surgery or neoplastic proliferation.

* C-reactive protein is test of choice in monitoring the acute

phase response, in monitoring patients with inflammatory joint

disease such as rheumatoid arthritis.

- The most widely used parameters in inflammation monitoring

are C-reactive protein and ESR (erythrocyte sedimentation Rate)

both will increase in inflammation.

Acute phase proteins:

1. 1-Antitrypsin (AAT)

- It is an acute phase reactant with antiprotease activity.

- Plasma concentrations rise two to three days after trauma or acute

infection.

- Its deficiency is associated with lung and liver disease.

- As a protease inhibitor, AAT acts against chymotrypsin, renin,

urokinase, plasmin and possibly thrombin, but the inhibition of

greatest clinical significance is directed against neutrophil elastase

and collagenase.

- The function of AAT is to neutralise lysosomal elastase released on

phagocytosis of particles by polymophonuclear leukocytes.

-AAT, being a relatively small molecule, can pass from capillaries into

tissue fluid, bind protease, and pass back into the intravascular fluid.

-low levels of AAT are found in

(1) neonatal respiratory distress syndrome,

(2) in sever protein-losing disorders and

(3) in congenital deficiency.

-Increased levels are more common because AAT is an

APR.

*The clinical consequences of inherited disorders of

1-antitrypsin synthesis.

- Inhaled particles and bacteria are continuously

removed from the lungs by leukocytes. This phagocytosis

gives rise to the release of elastase.

-When there is deficiency of AAT, the uninhibited enzyme

attacks and destroys the elastin of the alveolar wall.

-The loss of elasticity of the lung tissue results in

emphysema with impaired ventilation and susceptibility to

serious respiratory infections. The liver is also affected

-The condition may be aggravated by cigarette smoking, air

pollution or infection.

2. Haptoglobin acute phase protein

- Its function is to bind free haemoglobin released into the plasma

during intravascular haemolysis.

- The haemoglobin-haptoglobin complexes formed are removed

by the reticuloendothelial system

- Its components are metabolised to free a.a.s and iron

- Haptoglobin thus prevents loss of haemoglobin to urine and

conserves iron.

- Thus a low plasma haptoglobin concentration can be indicative

of intravascular haemolysis, or haemoglobin turnover, as occur

in haemolytic anaemias, transfusion reactions and malaria.

- Low concentrations due to decreased synthesis are seen in

chronic liver disease, metastatic disease and severe sepsis.

- Haptoglobin is an acute phase protein and its concentration also

increases in burns, nephrotic syndrome

3. Caeruloplasmin

- Caeruloplasmin is a late APR

- It is the principal copper-containing protein in plasma. It is a copper donor, another possible role of CER is as an antioxidant

- Once CER is synthesised, it neither gains nor loses copper unless metabolised.

-Plasma copper consists of a non-dialysable fraction (95%) attached to CER and of dialyzable (free) fraction (5%) loosely bound to albumin

and histidine.

-Copper is transported in the dialysable form from the gut to the liver; it is incorporated into the CER apoprotein, which is released into the

bloodstream.

- Increased absorption of copper leads to increased synthesis of CER and increased excretion of copper-protein complexes in the bile.

-Synthesis of CER thereby provides a first-line reaction to potential copper toxicity.

Wilson’s disease: CER deficiency

* It is rare condition where the plasma CER is typically reduced

free copper concentration is increased.

* Unless treated with copper chelators such as penicillamine, the

disease is always progressive and fatal and causes liver dysfunction.

The two fundamental disturbances could occur:

I) a gross decrease in the rate of incorporation of copper into apoprotein

II) a marked reduction in the biliary excretion of copper.

- Copper is deposited in the kidneys, in the liver (where it causes

cirrhosis) and in brain (where it damages the basal ganglia).

- Low plasma levels of CER are also found in malnutrition,

malabsorption, nephrosis and sever liver disease.

Exercise, pregnancy and by oestrogen-containing oral contraceptives

increase CER concentration.

ImmunoglobulinsImmunoglobulins

*Immunoglobulins are unique in their heterogenisity, in their

sites of synthesis and in the fact their synthesis is an

adaptive response to antigenic stimulation.

-The immunoglobulins are a group of plasma proteins that

function as antibodies, recognising and binding foreign

antigens.

-This facilitates the destruction of these antigens by elements

of the cellular immune system.

- Since every immunoglobulin molecule is specific for

one antigenic determinant, or epitope, there are vast

numbers of different immunoglobulins.

ImmunoglobulinsImmunoglobulins

*Most plasma proteins are synthesised in the liver.

*Immunoglobulins are synthesised and secreted by plasma

cells (mature B-lymphocyte, immunoglobulin producing

cells),

-These cells develop numerous receptor immunoglobulins

on their surface membranes.

Upon encountering antigen, these B-lymphocytes proliferate

and develop into plasma cells, each of which secretes into

the blood a highly specific antibody capable of binding

additional antigen.

*The stimulating antigen are normally foreign but may be on

host cell surfaces and cause autoimmune disease

* All Immunoglobulins share similar basic structure, consisting of two identical ‘heavy’ polypeptide chains and two identical ‘light’ chains, linked by disulphide bridges.

* There are five types of heavy chain ( Gamma, Alpha, Mu, Delta, Epsilon) and two types of light chain ( Kappa, Lambda),

* The immunoglobulin class

is determined by the type

of heavy chains.

* Light chains, are

produced independently

and in slight excess of their

incorporation into

immunoglobulins, their

constant regions have

different structures.

There are five types of heavy chain ( Gamma, Alpha, Mu, Delta, Epsilon) and two types of light chain ( Kappa, Lambda),

*The immunoglobulin class is determined by the type of heavy

chains.

IgG

- Is the most abundant immunoglobulin.

-It forms 65% of immunoglobulin in extravascular liquids and 70-75% of

serum Antibodies of the IgG class are produced in response to most

bacteria and viruses; they aggregate and coat small soluble foreign

proteins such as bacterial toxins.

- IgGs that are slightly different in the structure of their variable regions

IgA

-Approximately 10-15% of serum immunoglobulins is IgA

- Secretary IgA is found in tears, sweat, saliva, milk, colostrum (is the first

milk that breasts produce in the early days of breast feeding) and GI and

bronchial secretions.

- It is synthesised mainly by plasma cells in the mucous membranes

of the gut and bronchi and in the lactating breast.

- The secretary component makes IgA more resistant to enzymes and

protects the mucosa from bacteria and viruses.

- Its presence in colostrum and milk probably protects neonates from

intestinal infections.

IgD

- Accounts for less than 1% of serum immunoglobulins.

-Like IgD and IgM are surface receptors for antigen in B-

lymphocytes, but its primary function is unknown.

IgM

- Is the most ancient and least specialised immunoglobulin

-The only immunoglobulin that produced by neonate

- In adult serum, it is the third most abundant immunoglobulin and

accounts for 5-10% of the total circulating immunoglobulins.

- Most of IgM is a pentamer of five IgM monomers.

- Its high molecular weight prevents its passage into extravascular

spaces.

- B-lymphocytes at first have IgM surface receptors and secrete IgM

in the first or “primary” response to an antigen.

IgE

- Is rapidly and firmly bound to mast cells and only trace amounts

of it are normally present in serum.

- Each molecule may be a different antibody produced by a

different variable region.

- When antigen (allergen) cross-links two of the attached IgE

molecules, the mast cell is stimulated to release histamine and

other vasoactive amines.

- These amines are responsible for the vascular permeability and

smooth muscle contraction occurring in such allergic reactions as

hay fever, asthma, urticaria and eczema.

Immunoglobulins disorders

Increases and decreases of plasma immunoglobulin

concentrations can be either physiological or pathological in

origin.

Hypogammaglobulinaemia

Physiological causes

-At birth IgA and IgM concentrations are low and rise steadily,

- IgA may not reach the normal adult concentration until after the

end of the first decade.

- IgG is transported across the placenta during the last trimester of

pregnancy and levels are high at birth (except in premature

infants).

- The IgG concentration then declines, as maternal IgG is cleared

from the body, before rising again as it is slowly replaced by the

infant’s own IgG.

- Physiological hypogammaglobulinaemia is one of the reasons

for the susceptibility of infants (especially the premature) to

infection.

Pathological causes

-Various inherited disorders of immunoglobulin synthesis are

known defect or partial defect of only one or two

immunoglobulins.

- Complete absence of immunoglobulins (Bruton’s

disease) and affected children develop recurrent bacterial

infections,

- Acquired Hypogammaglobulinaemia resulted form

haematological malignancies, such as chronic lymphatic

leukaemia, multiple myeloma and Hodgkin’s disease.

- Hypogammaglobulinaemia can be a complication of the

use of cytotoxic drugs and is a feature of severe protein-

losing states, for example, the nephrotic syndrome and

increased catabolism

- Measurements of the specific class of immunoglobulin is

essential for the diagnosis of hypogammaglobulinaemia.

Hypergammaglobulinaemia

physiological causes

-Increased serum immunoglobulins can be seen in both acute and chronic infections.

- IgG tends to increase in most bacterial and viral infections

-IgA in skin, gut, respiratory and renal infections

- IgM in primary viral infections and bloodstream infections such as malaria.

- Chronic bacterial infections cause an increase in serum levels of all immunoglobulins.

Pathological causes

- IgG tends to predominate in autoimmune responses;

-IgG and other plasma immunoglobulin concentrations are increased in autoimmune diseases, for example, rheumatoid disease and systemic

lupus erythromatosus (SLE), and in chronic liver diseases which have an autoimmune basis.

*The measurement of an specific immunoglobulin is important for diagnosis of some infectious diseases; e.g., in chronic active hepatitis, IgG and

sometimes IgM are increased.

Estimations of IgE are used in the management of asthma and other allergic conditions, especially in children.

Monoclonal immunoglobulins (paraproteins)

-A single clone of plasma cells produces immunoglobulin molecules

with identical structures. If the clone is permitted to multiply, the

concentration of its particular protein in the patient’s serum becomes so

great.

- These monoclonal immunoglobulins, which are also called paraproteins,

may be polymers, monomers, or fragments of immunoglobulin

molecules; if fragments they are usually light chains (Bence Jones

proteins) or, rarely, heavy chains or half-molecules.

-Paraproteins (usually IgG or IgA) occur most frequently in multiple

myeloma (malignant proliferation of plasma cells).

-Since all molecules are identical, the paraprotein is seen on

electrophoresis as a separated band, usually in the -region. The urine

also must be examined because these proteins rapidly cleared into urine

-Detection of paraproteins (Bence Jones proteins) indicates the

presence of neoplastic plasma cells

- Paraproteins can also be benign, that is, not associated with malignant

disease. The incidence of benign paraproteinaemia increases with age.

The liver

-The liver is the largest organ in the human body; it weighs approximately 1.2 to 1.5 kg in the adult.

-The liver has a dual blood supply; the portal vein, which carries nutrient-rich blood from the capillary bed of the alimentary tract, and the hepatic artery, which carries well-oxygenated blood to the liver.

-Venous drainage from the liver occurs via the right and left hepatic veins.

-The liver is of vital importance in intermediary metabolism and in the detoxification and elimination of toxic substances.

Major functions of the liver

Carbohydrate metabolism: gluconeogenesis, glycogen synthesis & glycogenolysis

Fat metabolism: fatty acid synthesis, cholesterol synthesis & excretion, lipoprotein synthesis, ketogenesis and bile & synthesis 25-hydroxylation of vitamin D

Protein metabolism: synthesis of plasma proteins (including some coagulation factors but not immunoglobulins, urea synthesis

Hormone metabolism: metabolism and excretion of steroid hormones, metabolism of polypeptide hormones

Drugs and foreign compounds metabolism and excretion

Storage: glycogen vitamin A vitamin B12 iron

Metabolism and excretion of bilirubin

Excretion and detoxification function of the liver:

1. Bilirubin

2. Amino acids, which are deaminated in the liver. Amino groups, and the ammonia produced by intestinal bacterial action and absorbed into the

portal vein are converted to urea.

3. Cholesterol, which is excreted in the bile either unchanged or after conversion to bile acids.

4. Steroidal hormones, which are metabolised and inactivated by conjugation with glucuronate or sulphate and excreted in the urine in these

water-soluble forms.

5. Many drugs.

6. Toxins, the reticuloendothelial Kupffer cells in the hepatic sinusoids are well placed to extract toxic substances which have been absorbed from the

GIT.

Efficient excretion of the end-products of metabolism and of bilirubin depends on:

1. Normally functioning liver cells.

2. Normal blood flow through the liver.

3. Normal biliary ducts.

Simple damage to the liver may not obviously affects its activity since the liver has considerable functional reserve.

- So simple tests of liver function (e.g., plasma bilirubin and albumin concentrations) are insensitive indicators of liver disease, a fall in plasma albumin concentration could be attributed to advanced liver disease.

- Tests reflecting liver damage (measurements of the activities of hepatic enzymes in plasma) are used.

The most common disease processes affecting the liver are:

Hepatitis, with damage to liver cells.

Cirrhosis, in which increased fibrous tissue formation leads to shrinkage of the liver, decreased hepatocellular function and obstruction of bile flow.

Tumours, most frequently secondary; for example, metastases from cancers of the large bowel, stomach and bronchus.

-Patients with liver disease often present with characteristic symptoms and signs, but the clinical features may be non-specific and in some patients,

liver disease is discovered incidentally.

- Extrahepatic biliary disease may present with clinical features suggestive of liver disease may have secondary effects on the liver; for instance,

obstruction to the common bile duct may cause jaundice and, if prolonged, a form of cirrhosis.

Bilirubin metabolism

- Bilirubin is derived from the haem moiety of the haemoglobin, myglobin and

cytochrome moleculesHaem & PophyrinsPorphyrins: are cyclic compounds that bind metal ions usually Fe+2,Fe+3.-Heme: one ferrous ion coordinated in the center of porphyrins. -Heme is highly turned over: 6–7 gm is synthesized and destroyed dailyStructure of porphorins-Ring structure of 4 pyrrole rings linked with methylenyl bridge.-Side chains: different porphyrins vary of the side chain that are attached to pyrrole rings.

Bilirubin metabolism

- Bilirubin is derived from the haem moiety of the

haemoglobin, myglobin and cytochrome molecules

- Iron is reutilized

-RBC are taken up by liver and spleen and macrophages,

and

degraded by reticulo-endothelial system (RE)

Formation of bilirubin

-Degradation is catalyzed by microsomal heme

oxygenase enzyme of the ER cells.

-The enzyme add the –OH to the methylen bridge

oxidation CO and Fe+3 is released and the product is

Billiverdin then it is reduced into Billirubin.

Uptake of Billirubin by liver

- Billirubin is slightly soluble in water transported in the

blood through complexion to albumin, then taken by

hepatocytes.

Formation of Billirubin diglucuronide

- In hepatocytes, the solubility of Billirubin is increased

by addition of two molecules of Glucuronic acid catalyzed

by “Billirubin glucuronyl transferase” using UDP-

glucuronic acid.

Heme Degradation

Excretion of Billirubin into bile

- Conjugated bilirubin is water-soluble and is secreted actively into

the biliary canaliculi, eventually reaching the small intestine via the

ducts of the biliary system.

Secretion into the biliary canaliculi is the rate limiting step in

bilirubin metabolism

-Billirubin diglucuronide is hydrolyzed and reduced by bacteria in the

gut to yield urobillinogen.

Urobillinogen

Reabsorbed, go to kidneys and converted excreted as urobillinogen & urobillin (yellow color)

Most are oxidized by bacteria to stercobillin (brown color)

Jaundice

Jaundice: The yellow staining of tissues skin and sclera due to

bilirubin deposition, is a frequent feature of liver disease.

High level Bilirubin is toxic to CNS

The bilirubin normally present in plasma is mainly (approximately

95%) unconjugated; since it is protein bound, it is not filtered by

the renal glomeruli and, in health, bilirubin is not detectable in

the urine.

Bilirubinuria: appearance of bilirubin in urine reflects an

increase in the plasma concentration of conjugated bilirubin, and

is always pathological.

Clinical jaundice may not be seen unless the plasma bilirubin

concentration is more than two and half times the upper limit of

normal.

Hyperbilirubinaemia can be caused by increased production

of bilirubin, impaired metabolism, decreased excretion or even

combination.

Jaundice can be classified to:

An increased rate of bilirubin production exceeds normal excretory capacity of the liver (prehepatic jaundice)(Hemolytic jaundice: sickle cell anemia,

or malaria).

The normal load of bilirubin cannot be conjugated and/or excreted by damaged liver cells (hepatic jaundice). Hepatocellular Jaundice: liver

damage, cirrhosis, hepatitis.

The biliary flow is obstructed, so that conjugated bilirubin cannot be excreted into the intestine and is returned into the systemic circulation

(posthepatic jaundice) Obstructive jaundice: bile duct obstruction.

Biochemical assessment of liver function

Bilirubin ( total bilirobin 0.3-1.2 mg/dl)

Unconjugated hyperbilirubinaemia

-Unconjugated hyperbilirubinaemia occurs if there is:

A marked increase in the bilirubin load as a result of haemolysis, or of the breakdown of large amounts of blood after haemorrhage into the GIT. In haemolysis,

hyperbilirubinaemia is due to increased production of bilirubin, which exceeds the capacity of the liver to remove and conjugate the pigment.

- Unconjugated hyperbilirubinaemia is also can be associated to high urobilinogen. Haemolytic disease more bilirubin is excreted in the bile the amount of

urobilinogen entering the hepatic circulation increased and urinary urobilinogen is increased.

- As a result of haemolytic disease, the plasma concentration of unconjugated bilirubin may be as high as 500 mol/L (30 mg/dl) and exceeds the plasma protein-binding

capacity.

Impaired binding of bilirubin to ligand or impaired conjugation with glucuronate in the liver. Like in some liver disease.

It could be due to an inherited abnormality of bilirubin metabolism (defect in the conjugating enzyme) ’Gilbert’s syndrome’,

- Unconjugated bilirubin is normally totally bound to albumin. It not water soluble and therefore cannot be excreted in the urine.

- Patients with unconjugated hyperbilirubinaemia do not have bilirubinuria.

Conjugated hyperbilirubinaemia

-Due to leakage of bilirubin from either hepatocytes or the

biliary system into the bloodstream when its normal route

of excretion is blocked.

- The water-soluble conjugated bilirubin entering the

systemic circulation is excreted in the urine, giving it a

deep orange-brown colour.

- In complete biliary obstruction, no bilirubin reaches

the gut, no urobilin is formed and the stools are pale in

colour.

- Hyperbilirubinaemia can be due to an excess of both

conjugated and unconjugated bilirubin.

- Bilirubinuria is always pathological.

Jaundice in newborns

- It is physiological jaundice is defined as mild jaundice not present at birth, which develops during the first few days and

continues during the first week of life, and for which there is no obvious pathological reason.

- The transient ‘physiological’ jaundice of the new-borns reflects decrease in the activity of Billirubin glucuronyl transferase

-The activity increases rapidly.

-Jaundice during the first 24 hours of life is more likely to be pathological than physiological.

- Proportionally more unconjugated bilirubin reaches the liver in the newborn infant than in the adult because:

1. The red cell half-life is shorter; the blood haemoglobin concentration falls rapidly during the first week of life, even in normal

infants.

2. Delayed clamping of the umbilical cord may significantly increase red cell mass.

3. Damages may occur during birth haemoglobin breakdown increases the plasma bilirubin concentration.

- Newborns Newborns pathological Jaundicepathological Jaundice that diagnosed in during

the first 24 hours of life could occur due:

With excessive haemolysis, as in Rhesus incompatibility,

a lack of enzyme activity, as occurs in prematurity and in

Crigler-Najjar syndrome (the conjugating enzyme is severely

reduced).

- The high plasma level of unconjugated bilirubin leads to jaundice

and kernicterus (bilirubin encephalopathy)

- Bilirubin is destroyed by ultraviolet light and lesser degrees of

unconjugated hyperbilirubinaemia can be treated by

phototherapy. Water loss from the skin may be high and fluid

balance must be carefully monitored.

Methods for the determination of bilirubin

-The most widely used routine methods for bilirubin

measurements are photometric methods based on diazo

reaction.

- The diazo reagent reacts with bilirubin to produce colorimetric

dye.

- The fraction of bilirubin that reacted with the diazo reagent in

the absence of alcohol is called the direct bilirubin fraction

(conjugated).

-The indirect bilirubin (for Un-Conjugated) is used for the

difference between total bilirubin (found after the

addition of alcohol to the reaction mixture) and the

direct bilirubin fraction.

- Bilirubin levels in an adult in serum 0.3-1.2 mg/dl (5-21

mol/L), urine negative

- Conjugated bilirubin (direct) in serum 0- 0.2 mg/dl (0-3.4

mol/L)

Diseases of the Liver

1. Cholestasis: is any condition in which bile excretion from

the liver is blocked, which can occur either in the liver or in

the bile ducts.

Cholestasis may be either:

* Intrahepatic, in which bile secretion from the hepatocytes

into the canaliculi is impaired, due to: viral hepatitis; drugs

such as chlorpromazine or toxins such as alcohol;

inflammation of the biliary tract; autoimmune disease

(primary biliary cirrhosis); cystic fibrosis.

* Extrahepatic: due to obstruction to the flow of preformed

bile through the biliary tract by: biliary stones; inflammation

of the biliary tract; pressure on the tract from outside by

malignant tissue, usually of the head of the pancreas.

Diseases of the Liver

-Alkaline phosphatase activity is the most sensitive test for cholestasis.

*Increased synthesis of ALP in the affected ducts increases the activity of this enzyme in plasma.

* Patients with prolonged, cholestasis may present with severe jaundice and itching due to deposition of retained bile salts in the skin;

* Rarely there is bleeding due to malabsorption of vitamin K, with consequent prothrombin deficiency.

* Cholesterol retention may cause hypercholesterolaemia.

* Dark urine and pale stools suggest biliary retention of conjugated bilirubin,

2. Hepatitis:

a. Acute Hepatitis

Hepatitis is the Latin word for liver inflammation.

* It is characterized by the destruction of a number of liver

cells and the presence of inflammatory cells in the liver

tissue.

* Acute hepatitis is most frequently caused by infectious agents,

particularly viruses, and toxins.

* Some drugs and chemicals can cause acute hepatitis, including

alcohol, paracetamol and carbon tetrachloride.

* The viruses primarily associated with hepatitis are hepatitis A, B

and ‘non-A, non-B’ (principally hepatitis C virus)

-Most cases of viral hepatitis resolve completely.

Acute Hepatitis

-In severe cases, hepatic failure may develop, but most patients who

survive the acute illness eventually recover completely, and

transaminase activities return normal in ten to twelve weeks.

Patients may present with jaundice but this is often not apparent

early in the course of the disease.

- The biochemical findings in acute hepatitis are associated with

those of cell membrane damage with an increase in plasma ALT

activity greater than that of AST.

Hepatitis A (infectious hepatitis), an RNA enterovirus, spread by

contact with faecal matter, most often through ingestion of

contaminated food.

- Rarely fatal, it cannot be treated except by bed rest for 1–4

weeks, during which time no alcohol should be consumed.

- Infection with hepatitis A never leads to chronic disease.

- It may recur after 3 months.

Hepatitis B (serum hepatitis): Hepatitis B ranks as the ninth

leading killer in the world

* is spread through blood, semen, vaginal secretions, and saliva the

virus

* may take up to 6 months to incubate, and people may also become

asymptomatic carriers.

- Hepatitis B may heal slowly, and is a leading cause of chronic liver

disease and cirrhosis.

- Effective vaccines exist

Hepatitis C: remains in the blood for years and accounts for a large

percentage of cirrhosis, liver failure, and liver cancer cases.

Its main mode of transmission is through blood transfusion, and

possibly sexual intercourse

b. Chronic hepatitis

-Chronic hepatitis is defined as hepatic inflammation persisting without

improvement for six months.

Causes include autoimmune liver damage, chronic infection with

hepatitis B or C, alcohol and drugs.

*Chronic active hepatitis (is caused by active hepatocellular destruction

and usually progresses to cirrhosis, which may be present at the time

of diagnosis.

chronic active hepatitis may respond to treatment with immunosuppresive

or antiviral agents, according to its etiology,

*Chronic persistent hepatitis (a form of chronic hepatitis that is usually

benign, has good prognosis, not progressing to cirrhosis, and usually

asymptomatic without physical findings but with continuing abnormalities

of tests of liver status).

Plasma transaminase activities are elevated in all types, reflecting

the continuing hepatocellular damage.

ALP activity is usually normal.

Indices of synthetic function (albumin, prothrombin time) are

often abnormal in chronic active hepatitis but not in chronic

persistent hepatitis.

3. Cirrhosis3. Cirrhosis

- Progressive disease of the liver characterised by diffuse

damage to hepatic parenchymal cells, with nodular regeneration,

fibrosis, and disturbance of normal architecture;

-Associated with failure in the function of hepatic cells and

interference with blood flow in the liver, frequently resulting in

jaundice, portal hypertension, ascites, and ultimately hepatic

failure.

- Cirrhosis is the end result of many inflammatory and

metabolic diseases involving the liver, including prolonged toxic

damage due to alcohol.

-Causes of cirrhosis include chronic excessive alcohol intake,

autoimmune disease, persistence of hepatitis B or C virus and various

inherited metabolic diseases, such as Wilson’s disease,

haemochromatosis and 1-antitrypsin deficiency.

* Cirrhosis can be the cause of biochemical abnormalities decreased

albumin synthesis, decreased cholesterol synthesis, insulin resistance and

increased prothrombin time,

Prothrombin time (PT) is a blood test that measures how long it takes

blood to clot. It can be used to check for bleeding problems and for

monitoring the anticoagulant activities.

Prothrombin time, clotting time acute diseases

* Most of clotting factors are synthesized in the liver (Factor VII is an

important one) if there is any liver problem clotting time will be

increased

Factor VII is vit K dependent so in certain cases, the high prothrombine

time is not due to liver diseases but due to vit K deficiency

* Due to the great functional capacity of the liver, metabolic and clinical

abnormalities may not become apparent until late in the course of the

disease;

There are no reliable, simple biochemical tests to diagnose subclinical liver

disease.

CirrhosisCirrhosis

3. Tumors3. Tumors

-The liver is a common site for tumor metastasis.

- Primary liver tumors are rare and are associated with

cirrhosis, persistence of serological markers for

hepatitis B and C, and various carcinogens, including

aflatoxins.

- Plasma -fetoprotein is elevated at diagnosis in

approximately 70% of patients with primary

hepatocellular carcinomas and is a valuable marker for

this tumor although it can be increased, usually to a

lesser extent, in acute and chronic hepatitis and in

cirrhosis.

Liver Function Tests and Diseases

Liver function Tests

1) Testing of Bilirubin which indicates the excretory capacity of the

liver: prehepatic, hepatic, posthepatic jaundice

2) Testing of enzymes (ALT, AST, ALP and GGT)

ALT is more specific for liver, ALP can indicate the Cholestasis,

GGT is sensitive to liver diseases but non-specific

3) Testing of plasma proteins, which indicates the synthetic

capacity of the liver

Measurement of albumin conc chronic diseases

Prothrombin time, clotting time acute diseases

Polyclonal response in the Ig mainly IgG. When there is liver

cirrhosis of autoimmune origin high level of IgG

The End