Intraluminal pH modulates gastric prostaglandin synthesis

Prostaglandins play an important role in modulating gastric mucosal integrity and in regulating gastric acid secretion, but little is known regarding regulation of prostaglandin synthesis by the stomach. We have therefore examined the effects of changes in gastric intraluminal pH on the capacity of gastric tissue to synthesize prostaglandin E2. Oral administration of solutions with a pH of 8.3 or 10 markedly reduced the capacity of the gastric tissue to synthesize prostaglandin E2, but did not affect synthesis of leukotriene B4. This phenomenon was observed in three strains of rats. Administration of the same solutions subcutaneously did not affect gastric prostaglandin synthesis. On the 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 differences in the osmolarity of the test solutions. These studies suggest that changes in gastric intraluminal pH result in changes in gastric prostaglandin synthesis. It is possible that this represents a physiological response aimed at maintaining gastric mucosal integrity when intraluminal pH is low, while also providing a feedback inhibition of gastric acid secretion.