Which statement about aldosterone's renal effect is true?

Which statement about aldosterone's renal effect is true?

• A. It decreases sodium reabsorption in the distal nephron.
• B. It acts only on the proximal tubule.
• C. It increases sodium reabsorption and water reabsorption in the distal nephron.
• D. It has no effect on potassium handling.

Answer: (C)

Aldosterone’s main job in the kidney is to raise sodium reabsorption in the distal parts of the nephron, which in turn promotes water reabsorption and helps expand extracellular fluid. It does this by binding to mineralocorticoid receptors in principal cells, increasing the expression of apical ENaC channels and basolateral Na+/K+-ATPase pumps. As more Na+ is reabsorbed, a lumen-negative potential develops that drives K+ secretion into the tubule, increasing potassium excretion. Water follows the reabsorbed sodium when water channels are present, so distal nephron water reabsorption increases as well. So, the true statement reflects aldosterone’s effect of boosting sodium reabsorption and, indirectly, water reabsorption in the distal nephron. It does not decrease sodium reabsorption, it does not act only on the proximal tubule, and it does affect potassium handling by increasing its secretion.

Aldosterone’s main job in the kidney is to raise sodium reabsorption in the distal parts of the nephron, which in turn promotes water reabsorption and helps expand extracellular fluid. It does this by binding to mineralocorticoid receptors in principal cells, increasing the expression of apical ENaC channels and basolateral Na+/K+-ATPase pumps. As more Na+ is reabsorbed, a lumen-negative potential develops that drives K+ secretion into the tubule, increasing potassium excretion. Water follows the reabsorbed sodium when water channels are present, so distal nephron water reabsorption increases as well.

So, the true statement reflects aldosterone’s effect of boosting sodium reabsorption and, indirectly, water reabsorption in the distal nephron. It does not decrease sodium reabsorption, it does not act only on the proximal tubule, and it does affect potassium handling by increasing its secretion.