Bombesin stimulates human gastric function by gastrin-dependent and independent mechanisms.

Studies were performed in six men to determine the relationship between serum gastrin concentration and gastric function during exogenous and endogenous stimulation of gastrin release. When the intragastric pH was maintained at 5.0, there were dose-related increases in gastric acid secretion with increasing serum gastrin concentrations produced either by stepwise increasing doses of intravenous gastrin or bombesin, or by intragastric perfusion with peptone. When intragastric pH was maintained at 2.5, or when intravenous atropine was given hourly, sensitivity to both exogenous and endogenously released gastrin were similarly decreased. Gastric emptying was inhibited in a dose-dependent manner by both bombesin and peptone but not by exogenous gastrin. These results suggest that bombesin and peptone stimulate gastric acid secretion through release of circulating gastrin but inhibit gastric emptying by another mechanism.