Effect of omeprazole treatment on plasma concentrations of the gastric peptides, xenin, gastrin and somatostatin, and of pepsinogen.

The peptide xenin 25 is a gastric mucosal constituent like gastrin, somatostatin and pepsinogen. Gastrin and pepsinogen plasma concentrations increase when the secretion of gastric acid is reduced by proton pump inhibitors. In the present investigation, treatment with omeprazole led to an increase in fasting and postprandial plasma concentrations of xenin, gastrin and pepsinogens A and C (P < 0.05, in each instance), whereas somatostatin plasma levels remained unchanged. Because subcutaneous injection of pentagastrin did not raise xenin plasma concentrations, a direct effect of gastrin on xenin production seems unlikely. This study indicates that xenin plasma concentrations are regulated by intragastric pH, as are those of gastrin and pepsinogen.