Effect of blood pH on distal nephron hydrogen ion secretion

The purpose o this study was to determine the effect of changes in blood hydrogen ion concentrations on urine acidification. The urine minus the blood PCO2 gradient in alkaline urine was used to monitor distal nephron hydrogen ion secretion. To obtain alkaline urine during acidemia, we induced proximal renal tubular acidosis by lysine. The urine minus the blood PCO2 gradient was evaluated relative to the urine bicarbonate concentration over a range of blood pH values. For any given urine bicarbonate concentration, the urine minus the blood PCO2 gradient was directly related to the blood hydrogen ion concentration. Conclusions. Acidemia stimulates and alkalemia inhibits distal nephron hydrogen ion secretion. Because the slope relating the urine minus the blood PCO2 gradient to the urine bicarbonate concentration was much steeper in urine from acidemic dogs, this change in relationship cannot be explained by a simple chemical equilibrium of the bicarbonate buffer system.