INTRALUMINAL PH MODULATES GASTRIC PROSTAGLANDIN SYNTHESIS

Prostaglandins play an important role in modulating gastric mucosal in tegrity and in regulating gastric acid secretion, but little is known regarding regulation of prostaglandin synthesis by the stomach. We hav e therefore examined the effects of changes in gastric intraluminal pH on the capacity of gastric tissue to synthesize prostaglandin E(2). O ral administration of solutions with a pH of 8.3 or 10 markedly reduce d the capacity of the gastric tissue to synthesize prostaglandin E(2), but did not affect synthesis of leukotriene B-4. This phenomenon was observed in three strains of rats. Administration of the same solution s subcutaneously did not affect gastric prostaglandin synthesis. On th e other hand, oral administration of a solution of pH 1 significantly increased prostaglandin synthetic capacity, while a solution with a pH of 3 had no effect. The effects observed were not attributable to dif ferences in the osmolarity of the test solutions. These studies sugges t that changes in gastric intraluminal pH result in changes in gastric prostaglandin synthesis. It is possible that this represents a physio logical response aimed at maintaining gastric mucosal integrity when i ntraluminal pH is low, while also providing a feedback inhibition of g astric acid secretion.