Intravenous histamine reduces bombesin-stimulated gastrin release in dogs

The effect of histamine on gastrin release was studied in 7 conscious mongrel dogs with chronic gastric and duodenal fistulas. Histamine-2 HCl was infused in doses of 0 (control), 20, 40, 80, and 160 micrograms/kg per h for 2 h on separate days. During the second hour, bombesin 500 ng/kg per h was infused intravenously. Intragastric pH was constantly kept at 2.5 by intragastric titration during each test. Leakage of gastric contents into the duodenum was prevented by a prepyloric balloon passed retrograde through a duodenal fistula. Gastrin release, as expressed by the integrated response during the last 50 min of the bombesin infusion was significantly (P less than 0.05) decreased by all doses of histamine, compared to control. The infusion doses of histamine studied, 20, 40, 80, and 160 micrograms/kg per h reduced bombesin-stimulated gastrin release 16%, 19%, 19%, and 30%, respectively. This effect was blocked by a histamine H-2 but not an H-1 receptor antagonist. We conclude that by an H-2 mechanism, exogenous histamine reduces bombesin-stimulated gastrin release in dog.