Bombesin: a vagally independent stimulator of gastrin release

In this study we demonstrate that bombesin is a potent stimulant of canine gastrin and gastric acid secretion. Bombesin was shown to release almost fourfold more gastrin than a meal by a mechanism which is independent of vagal integrity. An exogenously administered cholinomimetic agent released only minimal amounts of gastrin after vagotomy and virtually none in the intact canine model. The combination of bombesin and bethanechol caused a significant increase in acid secretion compared with bombesin alone and was associated with a marked inhibition of gastrin release both before and after vagotomy. Gastric acid secretion in response to bombesin was not significantly altered by vagotomy. We interpret these data to reflect the sensitivity of bombesin-stimulated gastrin release to gastric luminal pH, although they also suggest the existence of a cholinergic inhibitory mechanism for gastrin release. The data provided by this study are consistent with the hypothesis that bombesin might function as a paracrine neuromodulator of gastrin release. in view of its presence in the nerves and mucosa of human stomach and its potent actions on gastrin release and gastric acid secretion, bombesin may play a role in gastric physiology.