Question

The Antihypertensive action of thiazide diuretics is attributed to which of the two factors?
1. Closing of calcium ion channels
2. Stimulation of adenylyl cyclase
3. Depletion of sodium ions
4. Decrease in peripheral resistance

• A. \( \text{(I) and (II)} \)
• B. \( \text{(II) and (III)} \)
• C. \( \text{(I) and (III)} \)
• D. \( \text{(III) and (IV)} \)

Hint:

Think of thiazides as "salt and vessel relaxers" for blood pressure control – they get rid of sodium and make blood vessels wider.

Answer 1

The Correct Option is D

Thiazide diuretics lower blood pressure through several mechanisms. Initially, they increase sodium and water excretion, leading to a decrease in extracellular fluid volume and thus reducing cardiac output. This corresponds to (III) Depletion of sodium ions. However, with chronic use, the reduction in blood pressure is primarily maintained by a decrease in peripheral vascular resistance. This occurs due to various factors, including vasodilation. Therefore, the two main factors contributing to the long-term antihypertensive action of thiazide diuretics are the depletion of sodium ions (leading to reduced blood volume initially) and a (IV) Decrease in peripheral resistance. Options (I) and (II) are not the primary mechanisms of the antihypertensive action of thiazide diuretics. Thiazides primarily affect sodium and chloride transport in the distal convoluted tubule of the nephron.