What is the primary function of the renal proximal tubule?

What is the primary function of the renal proximal tubule?

• A. Reabsorption of filtered glucose, amino acids, bicarbonate, water, and ions
• B. Secretion of potassium
• C. Secretion of hydrogen ions
• D. Production of renin

Answer: (A)

The proximal tubule’s main job is bulk reabsorption of the filtered load. It reclaims most of what is filtered — glucose and amino acids are reabsorbed through sodium-coupled transporters, bicarbonate is reabsorbed to help maintain acid-base balance, and water plus many ions follow the reabsorbed solutes back into the blood. This reabsorption is driven by sodium transport, which powers the reuptake of glucose and amino acids and allows water to follow osmotically. Hydrogen ion and potassium handling and other secretory processes do occur in the nephron, and renin is produced by specialized juxtaglomerular cells, but they are not the primary function of the proximal tubule.

The proximal tubule’s main job is bulk reabsorption of the filtered load. It reclaims most of what is filtered — glucose and amino acids are reabsorbed through sodium-coupled transporters, bicarbonate is reabsorbed to help maintain acid-base balance, and water plus many ions follow the reabsorbed solutes back into the blood. This reabsorption is driven by sodium transport, which powers the reuptake of glucose and amino acids and allows water to follow osmotically. Hydrogen ion and potassium handling and other secretory processes do occur in the nephron, and renin is produced by specialized juxtaglomerular cells, but they are not the primary function of the proximal tubule.