GASTRIC PROSTAGLANDIN-E(2) RECEPTORS ARE THE COMMON ANTISECRETORY TARGET OF MUCOSAL PROSTANOIDS

The gastric mucosa produces all principal prostaglandin (PG) types, but receptor binding studies in this tissue have as yet been performed exclusively with [H-3]PGE2. Therefore we compared the binding of different H-3-labelled prostanoids to fundic mucosal plasma membranes from the porcine stomach. Binding sites for [H-3]PGE2, [H-3]iloprost and [H-3]PGF2-alpha had similar nanomolar dissociation constants with high affinities for unlabelled PGE2. Iloprost and PGF2-alpha were 10- and 100-fold less potent competitors with Hill slopes near unity in all cases. In further [H-3]PGE2 competition studies the affinities of prostanoid ligands with selectivity for different PG receptor types correlated closely with their respective antisecretory potencies, as tested by [C-14]aminopyrine uptake in isolated porcine parietal cells. We conclude that parietal cell PGE2 receptors are the common antisecretory target for all prostanoid types in the porcine stomach. There was no evidence for other mucosal PG receptors possibly involved in acid secretion.