EFFECT OF HCL ON TRANSMEMBRANE POTENTIALS AND INTRACELLULAR PH IN RABBIT ESOPHAGEAL EPITHELIUM

Background/Aims: Acidification of the basolateral membrane by adding H Cl to the serosal solution of esophageal epithelium leads to more necr osis than acidification of the apical membrane by adding HCl to the lu minal 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 ex amined in rabbit esophageal cells by impalement with intracellular mic roelectrodes. Results: Lowering luminal pH to 3.0 had no effect on mem brane voltage and/or pH(i) in either luminally or serosally impaled ce lls, although a decline in both parameters occurred at pH 1.5 in lumin ally impaled cells. In contrast, lowering serosal pH from 7.4 to 3.0 p rogressively reduced membrane voltage and/or pH(i). Membrane depolariz ation at low pH(o) was inhibited by a high-potassium solution or bariu m and mimicked by lowering pH(i) (gassing with CO2) at neutral pH(o). Conclusions: Basolateral, but not apical, membranes of esophageal epit helial cells are highly permeable to H+, accounting for the greater su sceptibility to damage from exposure to serosal than luminal acid. Mem brane depolarization at low pH(o) is mediated by low pH(i) through inh ibition of basolateral membrane K+ conductance.