Effect of HCl on transmembrane potentials and intracellular pH in rabbit esophageal epithelium

Abstract

Background/Aims : Acidification of the basolateral membrane by adding HCl to the serosal solution of esophageal epithelium leads to more necrosis than acidification of the apical membrane by adding HCl to the luminal solution. The aim of this study was to examine the mechanism for this difference. Methods : The effect of low extracellular pH (pH o) (HCl) on intracellular pH (pH i) and transmembrane potentials was examined in rabbit esophageal cells by impalement with intracellular microelectrodes. Results : Lowering luminal pH to 3.0 had no effect on membrane voltage and/or pH i in either luminally or serosally impaled cells, although a decline in both parameters occurred at pH 1.5 in luminally impaled cells. In contrast, lowering serosal pH from 7.4 to 3.0 progressively reduced membrane voltage and/or pH i. Membrane depolarization at low pH o was inhibited by a high-potassium solution or barium and mimicked by lowering pH i (gassing with CO 2) at neutral pH o. Conclusions : Basolateral, but not apical, membranes of esophageal epithelial cells are highly permeable to H +, accounting for the greater susceptibility to damage from exposure to serosal than luminal acid. Membrane depolarization at low pH o is mediated by low pH i through inhibition of basolateral membrane K + conductance.