Measurement of intracellular pH in suspensions of renal tubules from potassium-depleted rats.

Intracellular pH was estimated from the fluorescence of 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein (BCECF) in isolated renal cortical tubules from control, potassium-depleted (KD) and NH4Cl-induced metabolic acidosis (MA) rats. While pHi was not different among control, short- and long-term KD, and NH4Cl MA rats, in vitro rates of ammonium production were increased in rats with metabolic acidosis and both short- and long-term potassium depletion. Mitochondrial matrix pH, and the pH gradient across the mitochondrial membrane were not different in tubules from KD rats compared to those from controls. These results are interpreted to indicate that a signal other than intracellular acidosis maintains the high rate of renal ammoniagenesis seen in KD.