Inhibition by somatostatin of gastrin release and gastric acid responses to meals and to pentagastrin in man.

The inhibitory actions of intravenous somatostatin on the gastric secretory responses to pentagastrin (1.5 microng/kg-h i.v.) and to a meal (10% peptone, pH 5.5) were studied in six healthy subjects. Meal-induced gastric acid output was estimated by means of a modified Fordtran and Walsh method of intragastric titration. Somatostatin (5 microng/kg-h; cyclic form) significantly inhibited the total 1-hour acid response to pentagastrin by about 70% (inhibition of pepsin secretion: about 70%) and that to a test meal by about 75%. During the last 30 min of somatostatin infusion the pentagastrin-stimulated secretion of acid was significantly reduced by about 90% (inhibition of pepsin output: about 85%) while the corresponding figure in the test with meal-induced secretion was about 95%. Serum gastric--elevated in response to the test meal--was found to be merely lowered by about 30% during somatostatin infusion. Consequently, it is tempting to assume that inhibition of human gastric acid secretion by exogenous somatostatin largely results from a direct antisecretory effect upon parietal cells and, only to a minor extent, from an indirect action via reduction of gastrin release.