Characteristics of basolateral Cl^- transport by gastric surface epithelium in Necturus antral mucosa

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 (a(Cl)/(i)). Our data indicate that 1) a(Cl)/(i) (range 12-25 mM) is close to that predicted if Cl^- is distributed across the cell membranes by electrochemical equilibrium, 2) a(Cl)/(i) 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 a(Cl)/(i), 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.