Which statement best describes aldosterone's effect?

Which statement best describes aldosterone's effect?

• A. It decreases sodium reabsorption in the distal tubule.
• B. It stimulates water excretion to lower blood pressure.
• C. It is released by the adrenal medulla in response to high blood pressure.
• D. It promotes sodium reabsorption in the distal tubule, increasing blood volume.

Answer: (D)

Aldosterone acts to conserve sodium in the kidney, which in turn pulls water back into the bloodstream. It’s produced by the adrenal cortex and released in response to signals from the renin-angiotensin-aldosterone system when blood pressure or sodium is low (or potassium is high). In the distal tubule and collecting duct, it increases the expression and activity of sodium channels (ENaC) and the Na+/K+-ATPase pump, so more Na+ is reabsorbed into the blood. Water follows the reabsorbed sodium osmotically, increasing extracellular fluid volume and blood pressure. This is why the statement that best describes aldosterone’s effect is that it promotes sodium reabsorption in the distal tubule, increasing blood volume. It also promotes potassium excretion as a related effect.

Aldosterone acts to conserve sodium in the kidney, which in turn pulls water back into the bloodstream. It’s produced by the adrenal cortex and released in response to signals from the renin-angiotensin-aldosterone system when blood pressure or sodium is low (or potassium is high). In the distal tubule and collecting duct, it increases the expression and activity of sodium channels (ENaC) and the Na+/K+-ATPase pump, so more Na+ is reabsorbed into the blood. Water follows the reabsorbed sodium osmotically, increasing extracellular fluid volume and blood pressure. This is why the statement that best describes aldosterone’s effect is that it promotes sodium reabsorption in the distal tubule, increasing blood volume. It also promotes potassium excretion as a related effect.