What effect does spironolactone have on sodium in the kidneys?

Spironolactone is a potassium-sparing diuretic that primarily acts on the distal convoluted tubules and collecting ducts of the kidneys. Its primary mechanism of action involves antagonism of the mineralocorticoid receptor, which is stimulated by aldosterone.

In cases of aldosterone activity, sodium is reabsorbed back into the bloodstream, leading to sodium retention. However, when spironolactone inhibits the effects of aldosterone, it reduces this sodium reabsorption, promoting the excretion of sodium in the urine. This mechanism not only aids in reducing fluid overload by allowing the kidneys to excrete more sodium and subsequently more water, but it also helps maintain potassium levels by preventing its excretion. Therefore, the correct answer is that spironolactone promotes sodium excretion in the kidneys.