9 December 2009Renal Physiology

Lab this week: UrinalysisReview website for

instructions. Bring handout with Data

sheet.Abstracts, Haiku, &

Golf Swing

Fig. 14.02a

Figure 14.17To be emphasized during Urinalysis Lab.

Countercurrent Multiplier & Countercurrent Exchange

4. Metabolism by tubular cells

Misleading diagram!Only 20% is filtered.

Inulin (exogenous) and Creatinine (endogenous) used to measure GFR.

Calculating clearance

Clearance of s = Urine concentration of s X Urine Volume Plasma concentration of s

• Clearance = volume of plasma from which a substance is completely removed (cleared) by the kidneys per unit time.

• Clearance of Inulin is 120 ml/min • Cinulin or Ccreatinine = Glomerular Filtration Rate

• If C x is greater than GFR ( which is Cinulin) then that substance undergoes NET TUBULAR SECRETION

• If C x is less than GFR ( which is Cinulin) then that substance undergoes NET TUBULAR REABSORPTION

Who Cares?

Fig. 14.04Fluid-filled cysts

Polycystic Kidney Disease

Fig. 14.10

Apical

Reabsorption and secretion in proximal tubule is NOT under hormonal control.Primary active transport of Na+ establishes a gradient for reabsorption of glucose, amino acids, etc.

Reabsorption and secretion in DCT & CCD is under hormonal control.Hormones that act here: ANH, ADH, Aldosterone.

Here, reabsorption of Na+ is linked to the secretion of K+.

Fig. 14.14

Glucose & amino acids

Glucose & a.a.s

Reabsorption of Na+ which begins with Na+/K+ ATPase in basolateral membrane is the first step in reabsorption of most substances.Cl- follows Na+, and these ions create an osmotic gradient in the basolateral clefts which is the driving force for reabsorption of water by diffusion (osmosis) and then bulk flow into peritubular capillaries.

Figure 14.11If plasma glucose concentration exceeds 200 mg/100 ml, glucose transporters are saturated and any additional filtered glucose will be lost in the urine.

Effect of Aldosterone: insertion of more Na+K+ATPase into basolateral membrane

Effect: Increase Na+ reab and Increase K+ Secretion

Figure 14.22

↑ plasma volume

How is secretion of Aldosterone affected by an ↑ plasma volume?

Important point:Hormone secretion is not all-or-nothing!Hormone secretion is “graded” and proportional.

Figure 14.30 Apply this information to each of the three Test Beverages used in the Urinalysis Lab!

Cell in the adrenal cortex that respond to AII are also receptors for plasma K+ concentration.

Sodium reabsorption and potassium secretion are coupled.