Final answer:
In the mammalian proximal convoluted tubule, sodium reabsorption is coupled with glucose and protons. Sodium ions are reabsorbed via an antiport mechanism with H+ and through cotransport with glucose.
Step-by-step explanation:
In the mammalian proximal convoluted tubule, sodium reabsorption is coupled with the reabsorption of glucose and protons. Sodium ions (Na+) are reabsorbed from the filtrate in exchange for hydrogen ions (H+) by an antiport mechanism in the apical membranes of cells lining the renal tubule. Additionally, sodium is also reabsorbed in conjunction with glucose through a cotransport mechanism, where the movement of sodium ions down their electrochemical gradient drives the uptake of glucose into the cells.
The proximal convoluted tubule plays a crucial role in reabsorbing ions, water, and nutrients; it also removes toxins and adjusts filtrate pH, making it a key site for reabsorption and secretion.