ion transport in renal physiology

Question 1

describe Na+ and bicarbonate reabsorption by proximal tubule

Answer 1

sodium pump creates a gradient and NHE brings Na+ into proximal tubule cell and H+ goes into lumen acidifying the filtrate. this forms carbonic acid which is converted to water and carbon dioxide by carbonic anhydrase. the co2 can readily diffuse so enters proximal tubule cell.
the kidney reabsorbs all of the bicarbonate filtered int the proximal tubule to retain base for pH buffers.

Question 2

what is amiloride and what are its effects

Answer 2

antihypertensive
inhibits NHE so inhibits Na+ reuptake into proximal tubule so continues in filtrate into urine.
Na+ excreted water follows—->excess production of urine
reduced Na+ re-entering blood, reduces water uptake, blood vol and thereby blood pressure.
blocks ENac in distal convoluted tubule.

Question 3

role of loop diuretics

Answer 3

antihypertensive
Block Na-K-Cl cotransporter
reduce uptake of Na+ across the thick ascending limb
1st point of treatment for mild hypertension

Question 4

Ca2+ reuptake by kidney

Answer 4

In distal convoluted tubule via NCX

Question 5

what is spironolactone used for

Answer 5

its a mineralocorticoid receptor antagonist used to treat hypertension caused by Hyperaldosteronism.
excess aldosterone leads to more expression of proteins so increased reuptake of Na+ in blood, increasing BP