Intracellular pH measurements in gastric mucosa.

Intracellular pH was measured in bullfrog gastric mucosa using a pH-indicator dye, bromthymol blue (BTB), with a spectrophotometric technique. Studies showed that BTB is taken up by the gastric mucosa and bound to intracellular components. The binding of BTB was shown to cause a shift in the pKa of the dye from the solution value of 6.95 to a value of 8.0. During the nonsecreting state, intracellular pH was estimated to be 7.4 (metiamide inhibition) or 7.1 (SCN inhibition). During active secretion of acid, intracellular pH increased with increasing secretion rates, reaching values in excess of pH 8. Using preparations from which the surface epithelial cells had been removed, it was shown that at least a portion of the alkaline response to stimulation occurs in the oxyntic or tubular cells. The results are interpreted in view of existing models for the chemical reaction involved in gastric acid secretion.