CHARACTERISTICS OF BASOLATERAL CL- TRANSPORT BY GASTRIC SURFACE EPITHELIUM IN NECTURUS ANTRAL MUCOSA

Conventional and ion-selective microelectrodes were used to characteri ze transport of Cl- across the basolateral cell membranes of gastric s urface epithelium in isolated preparations of gastric antrum of Nectur us. Conventional, voltage-sensing electrodes were used to evaluate cha nges in membrane potentials and resistances during removal of Cl- from the nutrient perfusate. Liquid ion exchanger Cl--selective microelect rodes were constructed and validated to measure intracellular Cl- acti vity (a(Cl)i). Our data indicate that 1) a(Cl)i (range 12-25 mM) is cl ose 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 mem brane 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 o f the inhibitor bumetanide, was demonstrated. These findings suggest t hat basolateral Na+-K+-Cl- cotransport is important in regulating cell Cl- levels in surface cells of the gastric antrum in Necturus.