**Core Concept**
Aldosterone antagonists, such as spironolactone, exert their effects by competing with aldosterone for binding to mineralocorticoid receptors in the collecting duct cells. This action is distinct from other diuretics that act on the luminal side of the renal tubules.

**Why the Correct Answer is Right**
Aldosterone antagonists do not act from the luminal side of the renal tubules. Instead, they affect the collecting duct cells by modulating the activity of the epithelial sodium channel (ENaC) indirectly. This results in increased sodium excretion and decreased potassium excretion. In contrast, other diuretics listed in the options (loop diuretics, ENaC blockers, and mannitol) act by inhibiting sodium reabsorption or increasing sodium excretion directly from the luminal side of the renal tubules.

**Why Each Wrong Option is Incorrect**
**Option A:** Loop diuretics, such as furosemide, inhibit the sodium-potassium-chloride cotransporter (NKCC2) in the thick ascending limb of the loop of Henle, thereby preventing sodium reabsorption and promoting diuresis from the luminal side.

**Option B:** ENaC blockers, such as amiloride, directly inhibit the epithelial sodium channel (ENaC) in the collecting duct cells, reducing sodium reabsorption and increasing sodium excretion from the luminal side.

**Option D:** Mannitol, an osmotic diuretic, increases the osmotic pressure of the tubular fluid, thereby preventing water reabsorption in the proximal convoluted tubule and loop of Henle. This promotes diuresis from the luminal side.

**Clinical Pearl / High-Yield Fact**
Aldosterone antagonists can cause hyperkalemia as a side effect due to their mechanism of action, which involves antagonizing the effects of aldosterone on potassium excretion.

**✓ Correct Answer:** C. Aldosterone antagonists