POTASSIUM CONDUCTANCE IN RABBIT ESOPHAGEAL EPITHELIUM

K+ conductance in apical and basolateral cell membranes of rabbit esop hageal epithelial cells was investigated within intact epithelium by i mpalement with conventional microelectrodes from luminal or serosal si des. Under steady-state conditions, K+ conductance was demonstrated in basolateral, but not apical, membranes by showing 1) membrane depolar ization upon exposure to either solutions high in K+ (20-65 mM) or con taining Ba2+, tetraethylammonium, or quinine, and 2) a resistance rati o that increased on exposure to high K+ solution and decreased on expo sure to Ba2+ , quinine, and tetraethylammonium. From exposures to high K+, the apparent K+ transference number and electromotive force gener ated at the basolateral membrane were calculated and found to be 0.42 +/- 0.01 and -83 +/- 3 mV, respectively. Furthermore, basolateral K+ c onductance was shown to be important for maintaining resting net trans epithelial Na+ absorption in that high K+ or barium inhibited the tran sepithelial potential difference and short-circuit current of Ussing-c hambered epithelia. We conclude that under steady-state conditions the basolateral, but not apical, membranes of esophageal epithelial cells contain a K+-conductive pathway and that this pathway is important fo r active sodium absorption.