Final answer:
Amiloride is a diuretic that blocks sodium channels in the collecting tubules of nephrons, thereby reducing sodium reabsorption and consequently decreasing potassium excretion. It does not act by blocking aldosterone receptors but indirectly reduces the effect of aldosterone on sodium and water reabsorption.
Step-by-step explanation:
The question pertains to the drug Amiloride, which is a medication used to manage hypertension and congestive heart failure. The correct description for Amiloride is B. Blocks luminal sodium channels in the collecting tubules. Amiloride acts by inhibiting the sodium channels on the luminal side of the epithelial cells in the collecting tubules of the nephron. This action reduces the reabsorption of sodium and, consequently, decreases potassium excretion because less sodium is available to exchange with potassium.
Aldosterone is a hormone that increases the excretion of potassium and reabsorption of sodium in the distal tubule of the kidneys. Amiloride, which is not an aldosterone antagonist, works by reducing the effects of aldosterone, without blocking aldosterone receptors. This is because the reduction in sodium reabsorption results in less water being reabsorbed, leading to a diuretic effect which helps in reducing blood pressure and edema.