Effect of bombesin on plasma insulin, pancreatic glucagon, and gut glucagon in man

The effect of bombesin on insulin, pancreatic glucagon, and gut glucagon was investigated in eight healthy volunteers and two pancreatectomized patients. Bombesin, infused iv at the constant rate of 5 ng kg -1, produced a sharp and statistically significant rise in the plasma insulin concentration. The peak was reached at 5 min (26 ± 2.17 μU/ml; P<0.005 vs. basal values), followed by a prolonged and statistically significant (P<0.05) decrease in blood glucose. Pancreatic glucagon rapidly rose to a maximal value of 80.5 ± 7.6 pmol/liter (P<0.005 vs. basal values). In contrast with the prompt increase in insulin and glucagon plasma levels, the peak in gut glucagon concentration (55.8 ± 4.6 pmol/liter; P<0.005 vs. basal values) was reached 30 min after bombesin infusion was discontinued. In the two pancreatectomized patients, bombesin induced an increase in gut glucagon concentrations only. The results presented indicate that bombesin acts directly on the A and B cells of the pancreas, influencing glucose homeostasis; however, more complex mechanisms seem to be involved in gut glucagon secretion.