Conventional and ion-selective microelectrodes were used to characterize transport of Cl- across the basolateral cell membranes of gastric surface epithelium in isolated preparations of gastric antrum of Necturus. Conventional, voltage-sensing electrodes were used to evaluate changes in membrane potentials and resistances during removal of Cl- from the nutrient perfusate. Liquid ion exchanger Cl(-)-selective microelectrodes were constructed and validated to measure intracellular Cl- activity (aiCl). Our data indicate that 1) aiCl (range 12-25 mM) is close to that predicted if Cl- is distributed across the cell membranes by electrochemical equilibrium, 2) aiCl is not influenced by changes in luminal Cl- content but is susceptible to changes in nutrient Cl- content, 3) Cl- conductances cannot be detected in the basolateral membrane and changes in membrane potentials do not influence aiCl, and 4) Cl- accumulation across the basolateral membrane depends on Na+ and the level of [K+] in the nutrient solution. Inhibition of K(+)-dependent Cl- accumulation, in the absence of nutrient Na+ or in the presence of the inhibitor bumetanide, was demonstrated. These findings suggest that basolateral Na(+)-K(+)-Cl- cotransport is important in regulating cell Cl- levels in surface cells of the gastric antrum in Necturus.
