Under aldosterone influence, which ion movement occurs in the distal nephron?

• A. Sodium reabsorption decreases.
• B. Potassium reabsorption increases.
• C. Sodium excretion increases.
• D. Sodium reabsorption increases; potassium secretion increases.

Answer: (D)

Aldosterone in the distal nephron boosts sodium reabsorption and promotes potassium secretion. It acts on principal cells, increasing the number and activity of epithelial sodium channels (ENaC) on the apical surface and the Na+/K+ ATPase pump on the basolateral side. This makes it easier for Na+ to move from the tubule into the blood, and to maintain that gradient, K+ is pushed into the tubule and excreted. Water often follows the reabsorbed Na+, supporting fluid retention. So the best description is that Na+ reabsorption increases while K+ secretion increases.