Effect of Simulated Systemic Administration of Aspirin, Salicylate, and Indomethacin on Amphibian Gastric Mucosa

The effects of 20 mM aspirin (ASA), 20 mM sodium salicylate (SA), or 10-4 M indomethacin placed in the nutrient solution (N) to stimulate systemic administration were investigated at pHN 7.3 in Ussingchambered amphibian gastric mucosae. In histamine-stimulated tissues, the initial rise and subsequent rapid fall in potential difference, rise in resistance, and inhibition of hydrogen ion (H+) secretion induced by SAN did not occur with ASAN unless hydrolysis of ASAN produced a SAN of >3 mM. In metiamide-treated tissues, 20 mM SAN caused an immediate fall in potential difference and an increase in resistance; 2 mM SAN and 20 mM ASA produced similar qualitative electrical changes, but only those induced by ASA were reversible. IndomethacinN caused no significant changes in potential difference, resistance, or H+ secretion in histamine- or metiamide-treated tissues. Despite producing highly significant reductions in generation of prostaglandin E2, and prostaglandin F2± and 6-keto prostaglandin F1α ASAN and indomethacin caused no surface ulceration. Sodium salicylate placed in the nutrient solution caused only a small reduction in prostaglandin F2α, without change in the other prostaglandins, and produced extensive edema in the lamina propria, histologically. We conclude the following: (a) The inhibition of H+ secretion and electrical changes caused by SAN in histamine-treated gastric fundus are not observed with ASAN unless there is hydrolysis to [SAN]>3 mM. (b) Our data strongly implicate the SAN in ASAN-containing solutions as being responsible for the electrical effects and inhibition of H+ secretion. (c) There is no correlation in vitro between inhibition of prostaglandin synthesis and the electrical or morphologic changes produced by nutrient exposure to ASA, SA, or indomethacin.