DISTRIBUTION OF PROSTAGLANDIN-E RECEPTORS IN THE RAT GASTROINTESTINAL-TRACT

Aims: in order to study the role of prostaglandin in the regulation of the gastrointestinal functions, gene expression of prostaglandin rece ptors along the rat gastrointestinal tracts were investigated. Methods : Rats were used for the study. The combination of counterflow elutria tion separation of mucosal cells and Northern blot analysis was used t o detect the gene expression of prostaglandin receptors in gastrointes tinal tracts. Results: In small intestine and colon, prostaglandin E2 EP1 and EP3 receptor mRNAs were mainly localized in the deeper intesti nal wall containing muscle layers. EP4 receptor gene expression, on th e other hand, was detected in the intestinal mucosal layer. In the sto mach, EP1 mRNA was detected in gastric muscle layers, whereas EP3 and EP4 receptor gene expression was mainly present in the gastric mucosal layer containing epithelial cells. In gastric epithelial cells, parie tal cells were found to have both EP3 and EP4 receptors. At lower conc entrations, prostaglandin E2 inhibited gastric acid secretion by parie tal cells probably through EP4 receptors. At higher concentrations, ho wever, it stimulated it. On the other hand mucous cells possessed only EP4 receptor mRNA. Conclusions: Thus, it is suggested that prostaglan din E2 modulates gastrointestinal functions through at least three dif ferent prostaglandin receptors (EP1, EP3, and EP4), each of which has a distinct distribution in the gastrointestinal tract. (C) 1997 Elsevi er Science Inc.