Evidence of cholecystokinin release by bombesin in the dog

Intravenous infusion of bombesin elicited in dogs a contraction of the gallbladder with decreased opening pressure of the choledocho duodenal junction and stimulation of pancreatic secretion. The pancreatic juice produced under the influence of bombesin was poor in bicarbonate and rich in protein. Threshold doses of the peptide were of the order of 0.25 μg kg-1h-1 and maximum protein output was obtained with 1 μg kg-1h-1. The pancreatic protein response to bombesin was very similar, in its onset and duration, to that elicited by intraduodenal infusion of L tryptophan. Infusions of bombesin repeated at short intervals produced tachyphylaxis. Antrectomy did not effect the stimulant action of bombesin on the pancreas. Atropine however, reduced the pancreatic protein response to bombesin. It is suggested that bombesin acts on the gallbladder and the exocrine pancreas through release of cholecystokinin from the duodenal mucosa. No release of secretin could be demonstrated. It is likely that the releasing activity of bombesin is limited, in the field of gastrointestinal peptides, to those belonging to the gastrin cholecystokinin family.