Which diuretic class inhibits NaCl reabsorption in the distal tubule?

• A. Loop diuretics
• B. Thiazide diuretics
• C. Potassium-sparing diuretics
• D. Carbonic anhydrase inhibitors

Answer: (B)

NaCl reabsorption in the distal tubule is carried out by the Na-Cl cotransporter on the apical membrane of the distal convoluted tubule. The thiazide class of diuretics specifically inhibits this transporter, reducing Na+ and Cl− reabsorption and increasing their excretion. That direct action in the distal convoluted tubule is why thiazides are the diuretic class that inhibits NaCl reabsorption there.

Loop diuretics act on the Na-K-2Cl cotransporter in the thick ascending limb, carbonic anhydrase inhibitors affect bicarbonate handling in the proximal tubule, and potassium-sparing diuretics work in the collecting duct (either by blocking ENaC or antagonizing aldosterone), not by inhibiting the Na-Cl cotransporter in the distal tubule.