Intracellular pH of gastric surface epithelial cells exposed to HCl and ethanol

Ultramicro-pH electrodes were used to determine intracellular pH changes induced by luminal perfusion of acid and alcohol in the gastric mucosa. In preparations of the bullfrog antral mucosa mounted on a horizontal type Ussing chamber, we determined intracellular pH (pHi) in situ of the surface epithelial cells exposed to HCl in the presence or absence of 10% ethanol in the luminal side. The pHi and apical membrane potential (LEM) of the surface epithelial cells were measured with double-barreled liquid ion-exchanger pH microelectrodes. In normal control conditions, the mucosal pHi was 7.43 +/- 0.01 and LEM was 29.5 +/- 0.7 mV (SE, n = 54). Acidification of luminal perfusate to pH 3.5 had no influence on pHi. Exposure to luminal 1 mM HCl (luminal pH: pHL = 3.1) lowered pHi to 7.31 +/- 0.01 (n = 6). Addition of 10% ethanol (EtOH) to luminal perfusate at pH 4.2 (0.1 mM HCl) led to immediate and progressive acidification of pHi (delta pHi = 0.12 +/- 0.02, n = 6). Hyperpolarization of LEM (by several mV) was also observed under such conditions, indicating an altered ion permeability of the apical membrane. These results suggest that even a low concentration of alcohol added to the gastric lumen causes a significant change in the surface epithelial cells, and this change becomes manifest when the luminal fluid is acidified to pH lower than 4.