Spironolactone antagonizes the action of which hormone?

• A. Aldosterone
• B. Angiotensin II
• C. Vasopressin
• D. Epinephrine

Answer: (A)

Spironolactone acts by blocking the mineralocorticoid receptor in the kidney, which is the receptor aldosterone binds to. In the collecting ducts and distal tubules, aldosterone normally increases sodium reabsorption and potassium excretion by upregulating channels and pumps (like ENaC and Na+/K+-ATPase). When spironolactone blocks this receptor, aldosterone’s effects are blunted, leading to less sodium reabsorption and potassium retention. This is why spironolactone is described as an aldosterone antagonist.

It doesn’t directly block the actions of angiotensin II, vasopressin, or epinephrine, which act through other receptors and pathways.