Effects of antiinflammatory agents and prostaglandins on acid and bicarbonate secretions in the amphibian-isolated gastric mucosa

Abstract

Effects of antiinflammatory agents and prostaglandins on H+ and HCO-3 secretions and electrical properties were investigated in the amphibian-isolated gastric mucosa. Gastric HCO-3 transport was studied in Rana temporaria fundus, in which H+ secretion had been inhibited with the histamine H2-receptor antagonists metiamide or cimetidine (10(-3) M), and in Necturus antrum, which secreted HCO-3 spontaneously. Hydrocortisone (100-500 microgram/ml) had no effect on H+ or HCO-3 secretion in the fundus. Indomethacin (10(-4) M) was a considerably more potent inhibitor of HCO-3 secretion than of H+ secretion in the fundus and also inhibited HCO-3 transport in the antrum. Fenclofenac (3 x 10(-3) M) almost abolished fundic HCO-3 transport and also depressed H+ secretion. There was a marked fall in transmucosal potential difference and a decrease in electrical resistance in fenclofenac-treated mucosae whereas indomethacin had less effect on electrical properties at the concentrations used here. The prostaglandins, E2, 16,16-dimethyl E2 and I2 all inhibited H+ secretion but only 16,16-dimethyl E2 stimulated HCO-3 secretion. The inhibitory action of indomethacin on HCO-3 secretion was prevented by co-administration of 16,16-dimethyl PGE2 (10(-6) M). It is proposed that the inhibitory action of nonsteroidal antiinflammatory drugs and the stimulatory action of some prostaglandins on HCO-3 secretion contributes to their ulcerogenic and anti-ulcer actions on the gastric mucosa.