Relationship between luminal Na+/H+ exchange and luminal K+ conductance in diluting segment of frog kidney.

Experiments were performed in the isolated perfused kidney of K+ adapted Rana pipiens to investigate the relationship between luminal K+ conductance and H+ transport in cells of the diluting segment. Inhibition of luminal Na+/H+ exchange by amiloride or by omission of luminal Na+ blocked luminal K+ conductance. Acidification of the kidney perfusate by elevation of pCO2 also reduced luminal K+ conductance. This effect could be prevented by furosemide. Since the steepest transcellular Na+ potential difference, directed from the lumen into the cell, is found when luminal Na+/Cl-/K+ cotransport is inhibited by furosemide, we conclude that luminal Na+/H+ exchange is most efficient at these conditions and thus could attenuate intracellular acidification.