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 while sparing potassium. This action is crucial in managing conditions like heart failure and hypertension.
**Why the Correct Answer is Right**
Amiloride works by blocking the epithelial sodium channel (ENaC) on the apical surface of principal cells in the collecting ducts. This channel is responsible for reabsorbing sodium ions, and its blockade leads to increased sodium excretion. However, since potassium reabsorption is also dependent on sodium reabsorption, blocking ENaC reduces potassium reabsorption, potentially leading to hyperkalemia. This effect is more pronounced in patients with renal impairment, where the kidneys' ability to excrete potassium is already compromised.
**Why Each Wrong Option is Incorrect**
**Option A:** This is not a correct description of amiloride's mechanism of action. Amiloride does not primarily act on the distal convoluted tubule (DCT), which is responsible for calcium reabsorption.
**Option B:** This option is incorrect because amiloride does not primarily act on the proximal convoluted tubule (PCT), which is responsible for glucose and amino acid reabsorption.
**Option C:** This option is incorrect because amiloride does not primarily act on the loop of Henle, which is responsible for chloride and sodium reabsorption.
**Clinical Pearl / High-Yield Fact**
Amiloride's potassium-sparing effect can be beneficial in patients with heart failure, but it requires careful monitoring of potassium levels, especially in patients with renal impairment.
**Correct Answer:** C.