Furosemide (Lasix) primarily acts on which segment of the nephron?

Furosemide (Lasix) is a loop diuretic that primarily acts on the ascending Loop of Henle within the nephron. This specific segment is critical in the reabsorption of sodium, potassium, and chloride ions. Furosemide inhibits the Na⁺-K⁺-2Cl⁻ cotransporter located on the luminal membrane of the epithelial cells in the thick ascending limb. By blocking this transporter, furosemide effectively prevents the reabsorption of these ions, leading to increased excretion of sodium, calcium, magnesium, and water.

This mechanism is important for its diuretic effect, as it disrupts the concentration gradient that the kidneys rely on to reabsorb water and solutes, promoting diuresis and helping in conditions like edema or hypertension.

In contrast, other segments of the nephron such as the proximal convoluted tubule, descending Loop of Henle, and distal convoluted tubule, do not primarily engage with furosemide’s action mechanism. The proximal tubule mainly reabsorbs a significant amount of sodium and bicarbonate, while the descending limb is primarily permeable to water and not significantly involved in the sodium reabsorption that furo