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MAGNESIUM

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INTRODUCTION

It is a macromineral

The eighth most abundant element in theearths crust

The fourth most abundant cation in body.

The second abundant intracellular cation.

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Functions

It is involved in more than 300 essential metabolicreactions.

Helps in ATP utilisation- MgATP

Play a critical role in second messenger system

CAMP is formed from MgATP and adenyl cyclase is

activated by Mg.Acts as an important physiological regulator of phospholipaseC.

Its is a non competitive inhibitor of IP3 inducedcalcium release .

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Cont

MODIFIES NUCLEIC ACIDSRibose phosphate structure of nucleic acids

binds to Mg with high affinity- results instabilisation of DNA and RNA.

Induces physiochemical changes that affect DNAmaintainence,duplication,transcription.

STABILISES MEMBRANES

Reacts with hydrophilic polyanions to stabilisethe membranes and thereby affects fluidity andpermeability.

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Cont..

ION CHANNELS

A regulator of Na+, K+ and Ca++ channels

Mg regulates Mg sensitive K+ channels in

skeletal and heart muscle .

Mg IS A NATURAL CALCIUM CHANNELBLOCKER.

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REFERENCE INTERVALS

Serum magnesium levels-1.7-2.4 mg/dl

RBC magnesium levels-2.3-7.3 mg/dl.

Serum or heparanised plasma preferred.

Anticoagulants such as citrate, oxalate,EDTA

should not be used.

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BIOAVAILABILITY

Calcium intake does not significantly affect

Mg absorption or retention.

Phosphorus, zinc, dietary fibres ,fatty acids

decreases absorption.

Parathyroid harmone, vit-D,growth harmone,

high protein intake, neomycin therapy

increases absorption.

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Daily Requirement (RDA)

ADULT MEN 19 to 30 400mg

31 yrs and older 420mg

ADULT WOMEN 19 to 30 310mg 31 yrs and older 320mg

Pregnancy 400mg

Lactation 400mg

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CONT.

ABSORPTION- in jejunum and ileum through

passive paracellular mechanism

In normal diet 30-40% absorbed.

Kidney- critical organ regulating Mg

homeostasis.

Bone-important reservoir of magnesium .

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REGULATION

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ASSESSMENT

Atomic absorption spectrophotometry-

REFERENCE METHOD

ISE

NMR

Mg isotopes.

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BIOLOGIC INDICATORS

Total serum magnesium

Ionised serum magnesium

Urinary magnesium excretion .

Magnesium load test.

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CAUSES OF DEFICIENCY

Gastrointestinal disorders

R

enal disorders

Drugs-diuretics,cisplatin, amphotericin B.

Metabolic acidosis

Diabetes mellitus-The vicious cycle

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CLINICAL MANIFESTATIONS OF

MAGNESIUM DEFICIENCY

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HYPOCALCEMIA

Mg causes disturbances in the mineralhomeostasis.

Impairs parathyroid gland functions by affecting

its second messenger system.

Impairs the ability of the kidney to synthesis

vit-D

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HYPOKALEMIA

Mg deficiency increases urinary K+ loss.

Increases the efflux of k+ from the Mg sensitive

K+ channel

Resting membrane potential of the heart is

disturbed

CARDIAC DYSRHYTHMIAS

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NEUROMUSCULAR MANIFESTATIONS

Mg -neuromuscular hyperexcitablity.

Latent tetany-+chvostek sign,Troussaeu

sign,carpopedal spasm.

Generalised seizures, muscular tremor

weakness and wasting.

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CHRONIC MAGNESIUM DEFICIENCY

HYPERTENSION

Decreases PG-I2 synthesis

Increases vasocontrictive effect of angiotensin II

and norepinephrine.

Platelet aggregation due the release of TX A2

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CONT

ATHEROSCLEROTIC VASCULAR DISEASES.

PRE-ECCLAMPSIA.

OSTEOPOROSIS.

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THANK YOU