Potassium-sparing diuretics interfere with which pump?

• A. Sodium-glucose transporter in proximal tubule
• B. Sodium-potassium pump controlled by aldosterone
• C. Chloride transporter in the loop of Henle
• D. Aquaporin channels in collecting ducts

Answer: (B)

Potassium-sparing diuretics work by blunting aldosterone’s action in the collecting duct, which reduces the activity of the Na+/K+-ATPase pump on the basolateral membrane and the ENaC channels on the apical side. Aldosterone normally promotes Na+ reabsorption and K+ secretion by upregulating these transporters; when this signaling is blocked, less Na+ is reabsorbed and less K+ is secreted, so potassium is spared. Drugs like spironolactone and eplerenone block aldosterone receptors, while amiloride and triamterene directly inhibit ENaC channels, all effectively reducing K+ loss.

This differs from targets like the sodium-glucose transporter in the proximal tubule, the chloride transporter in the loop of Henle, or aquaporin channels in collecting ducts, which are not the mechanisms through which potassium-sparing diuretics preserve potassium.