Reabsorption of sodium in the distal tubule is coupled to ?
A)Cl^ - reabsorption
B)H^+ reabsorption
C)K^ + reabsorption
D)water secration
E)K^ + secretion
A) Cl^- reabsorption
The correct answer is C) K^+ reabsorption.
In the distal tubule, reabsorption of sodium is closely coupled to the reabsorption of potassium (K^+). When sodium is reabsorbed, potassium is simultaneously secreted into the tubule for excretion. This process is known as sodium-potassium exchange. The reabsorption of sodium creates an electrochemical gradient that allows potassium to be reabsorbed from the tubular fluid back into the blood.
Option A) Cl^- reabsorption is not directly coupled to the reabsorption of sodium in the distal tubule.
Option B) H^+ reabsorption is not directly coupled to the reabsorption of sodium in the distal tubule.
Option D) Water secretion is not coupled to the reabsorption of sodium in the distal tubule.
Option E) K^+ secretion is the opposite process, where potassium is actively secreted into the tubular fluid. It is not directly coupled to the reabsorption of sodium in the distal tubule.
Therefore, the correct answer is C) K^+ reabsorption.