Effects of bile salts and prostaglandins on sodium transport in isolated rat gastric mucosa.

To determine whether prostaglandins may protect against bile salt inhibition of ion transport in the stomach, gastric mucosal tissue was isolated from the rat and mounted in flux chambers. Transport of Na+ was traced with radioisotopes in the absence of bile salts and then in the presence of conjugated taurocholate or unconjugated deoxycholate at low, intermediate and high mucosal concentrations (1, 5 and 15 mmol/1). At a high (7.40) or low (3.4) mucosal pH, only the unconjugated deoxycholate inhibited active Na+ transport from mucosa to submucosa with respect to untreated controls. Inhibition of Na+ transport was apparent at a low level of deoxycholate, which also inhibited the electrical potential difference. Intermediate and high levels of deoxycholate lowered the tissue resistance. When the tissues were exposed to mucosal prostaglandin E2 or its 16,16-dimethyl analogue before and during acidified taurocholate administration, Na+ transport was not changed significantly but the electrical resistance remained high. Thus, unconjugated bile salt is more potent than conjugated bile salt in inhibiting Na+ transport and breaking the gastric mucosal barrier, and prostaglandins may afford some small protection.