Influence of the route of administration of prostaglandin E1 on rat gastric secretion.

Changes in gastric secretion induced by the subcutaneous, intraduodenal or intragastric administration of prostaglandin E 1 (PGE1) were evaluated in pylorus-ligated rats. Subcutaneous and intraduodenal 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 PGE1 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 same mechanism of action when given subcutaneously or into the duodenum, while the effects observed after gastric administration are consequences of local actions. The difference in potency of PGE1 given subcutaneously and in the duodenum would seem to be due to differences in absorption from the site of administration and/or to a greater metabolism of PGE1 during its absorption from the intestines.