Question

The action(s) of aldosterone is (are) to

promote renal reabsorption of water.

promote renal excretion of potassium.

promote renal reabsorption of sodium.

All apply.

Answer 1

Answer) All apply

Aldosterone promotes renal reabsorption of sodium and water and also renal excretion of potassium.

Explanation - Aldosterone is a mineralocorticoid which is secreted by zona glomerulosa zone of adrenal cortex.

A fall in glomerular blood flow /glomerular blood pressure /glomerular filtration rate stimulates the adrenal cortex to release aldosterone.

Actions - Aldosterone acts on principal cells of distal convoluted tubule (DCT) and collecting duct (CD) of nephron in the kidneys to cause increase in sodium reabsorption in exchange for potassium and hydrogen ions which are then excreted in urine.

Aldosterone increases membrane permeability of principal cells of DCT and CT to sodium from the tubular lumen due to increased activity and synthesis of epithethial sodium channels (ENaCs).

This causes sodium reabsorption passively along the electrical and concentration gradients.

Aldosterone, by stimulating sodium reabsorption it also causes water retention by increasing water reabsorption from DCT and CT.

As sodium reabsorption occurs in exchange for potassium, so potassium ions are secreted into the DCT and CT and then excreted out through urine.

It leads to increase in blood pressure and glomerular filtration rate.