Amiloride can cause hyperkalemia due to its action on:
**Core Concept**
Amiloride is a potassium-sparing diuretic that acts on the collecting ducts of the kidneys to inhibit sodium reabsorption. This action is mediated by its binding to the epithelial sodium channel (ENaC), which is responsible for sodium reabsorption in the collecting ducts.
**Why the Correct Answer is Right**
The correct answer is related to the mechanism of action of amiloride. By inhibiting ENaC, amiloride reduces sodium reabsorption in the collecting ducts. To maintain electrical neutrality, the reabsorbed sodium ions are accompanied by potassium ions. However, when sodium reabsorption is blocked by amiloride, the potassium ions that are normally reabsorbed with sodium remain in the lumen and are excreted in the urine. This leads to an increase in potassium excretion and a decrease in potassium reabsorption, resulting in hyperkalemia.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the mechanism of action of amiloride and its effect on potassium levels.
* **Option B:** This option is incorrect because amiloride does not act on the Na+/K+-ATPase pump, which is responsible for sodium and potassium reabsorption in the distal convoluted tubule, not the collecting ducts.
* **Option D:** This option is incorrect because amiloride does not increase the activity of the Na+/K+-ATPase pump, which would lead to increased sodium and potassium reabsorption.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that potassium-sparing diuretics like amiloride can cause hyperkalemia, especially in patients with impaired renal function or those taking other medications that affect potassium levels.
**Correct Answer:** C.