[Intracellular pH of surface epithelial cells and the movement of bicarbonate ions under acid-base imbalance in gastric mucosa].

To investigate the effect of the acid-base imbalance on the gastric mucosal defense mechanism, the intracellular pH of gastric surface epithelial cells were measured with double-barreled H+ selective microelectrodes in the isolated antral mucosa of bullfrog stomach. By knowing the intracellular pH and the PCO2 of the serosal perfusate, the intracellular HCO3- concentration was estimated, and the rate of HCO3- secretion was directly measured with the pH-stat method in mounted preparations on a Ussing's chamber. Both the calculated intracellular HCO3- concentration and the rate of HCO3- secretion were dependent on the exogenous HCO3- supplied from the serosal perfusate. The alkaline tide raised the intracellular HCO3- concentration, thus increasing the mucosal buffering power against acid. Under mild respiratory acidosis, the production of endogenous HCO3- from the serosal CO2 was enhanced, and both the intracellular HCO3- concentration and the rate of HCO3- secretion were increased. As a result, the intracellular pH was maintained at a physiologically optimal level, and the ability of gastric mucosal protection was strengthened by enrichment of cellular bicarbonate supply. It is confirmed in this study that the maintenance of acid-base status in the cell is indispensable in the protection of gastric mucosa against acid invasion.