Acetazolamide primarily targets which segment of the nephron?

Acetazolamide primarily targets the proximal convoluted tubule of the nephron, which is responsible for a significant portion of sodium bicarbonate reabsorption. This carbonic anhydrase inhibitor works by inhibiting the enzyme that catalyzes the conversion of carbon dioxide and water to carbonic acid, leading to a decrease in the availability of hydrogen ions for bicarbonate reabsorption. As a result, there is an increased excretion of bicarbonate in the urine, which can lead to a mild metabolic acidosis.

In the proximal convoluted tubule, the reabsorption of bicarbonate is a crucial process for maintaining acid-base balance. By inhibiting this reabsorption, acetazolamide effectively alters fluid and electrolyte balance in the body. This mechanism is key in treating conditions like glaucoma, altitude sickness, and certain types of edema, where fluid management is essential.

Other segments of the nephron, such as the descending Loop of Henle, ascending Loop of Henle, and collecting duct, have different transport mechanisms and do not primarily utilize carbonic anhydrase in the same way, making acetazolamide's primary action specific to the proximal convoluted tubule.