Decrease in blood glucose and release of gut glucagon-like immunoreactive materials by bombesin infusion in the dog

Synthetic bombesin (100 ng/min) was infused under pentobarbital anesthesia in normal dogs and in insulin deprived depancreatized dogs 4 days after surgery. The release of gut glucagon-like immunoreactive materials (gut GLI) calculated as the difference between the values measured using cross-reacting antiserum and a so-called pancreatic glucagon specific antiserum was markedly stimulated by bombesin infusion. Plasma glucagon immunoreactivity (GI) measured by pancreatic glucagon specific antiserum also showed a small increase, whereas plasma glucose decreased significantly with a transient rise in insulin. The plasma glucose level did not decrease in depancreatized dogs. Gut GLI response in the regional mesenteric vein to 5% glucose administered into the loop of the ileum was strongly augmented by bombesin infusion. It is concluded that (1) bombesin infusion decreased blood glucose level in normal dogs but not in depancreatized dogs. (2) Bombesin infusion markedly augmented the release of GLI from the intestine. (3) Bombesin also stimulated the release of glucagon which was probably of gastrointestinal origin. (4) Insulin release was stimulated transiently by bombesin infusion. Thus, a competition of gut GLI with glucagon at the glucagon receptor site may be an explanation of the reduction in blood glucose.