PROSTAGLANDINS INFLUENCE OF THE ROUTE OF ADMINISTRATION OF PROSTAGLANDIN E 1 ON RAT GASTRIC SECRETION ENRIQUE HONG and CARMENLOPEZ Instituto Miles de Terap~utica Experimental Calzada Xochimilco 77 M~xico 22, D.F., M~xico ABSTRACT Changes in gastric secretion induced by the subcutaneous, intra- duodenal or intragastric administration of prostaglandin E I (PGEI) were evaluated in pylorus-ligated rats. Subcutaneous and intraduode- nal injections produced a dose-related inhibition in both total acid and volume of gastric secretion. Dose-response curves for inhibition obtained by these routes were parallel, although PGE 1 was more potent when given subcutaneously. Gastric administration produced a dose- related decrease in acid and an increase in volume. The slope of the dose-response curve for acid inhibition with this route was flatter than with subcutaneous or intraduodenal administrations. The present results suggest that PGE1 inhibits gastric secretion by the sameme- chanism of action when given subcutaneously or into the duodenum, while the effects observed after gastric administration are consequen- ces of local actions. The difference in potency of PGE l given subcu- taneously and in the duodenumwould seemto be due to dlfferences in absorption from the site of administration and/or to a greater meta- bolism of PGE 1 during its absorption from the intestines. APRIL 1977 VOL. 13 NO. 4 691