Effect of Bombesin on Plasma Insulin, Pancreatic Glucagon, and Gut Glucagon in Man*

Abstract

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 min-1, produced a sharp and statistically significant rise in the plasma insulin concentration. The peak was reached at 5 min (26 +/- 2.17 microU/ml; P less than 0.005 vs. basal values), followed by a prolonged and statistically significant (P less than 0.05) decrease in blood glucose. Pancreatic glucagon rapidly rose to a maximal value of 80.5 +/- 7.6 pmol/liter (P less than 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 less than 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.

Gastric acid secretion, intraduodenal pH and gastroenteropancreatic hormone release to bombesin in antrocolic transposition dogs.

“…The fact that motilin, insulin and glucagon levels increased during and after bombesin stimulation in both groups is in agreement with previous results in man (Ghatei et al 1982;Bruzzone et al 1983) and in dogs (Schusdziarra et al 1980;McDonald et al 1981;`Taysse et al 1981;McDonald et al 1983). A rise in insulin is not secondary to a rise in glucose, since the plasma glucose does not increase.…”

Bombesin stimulates insulin secretion by a pancreatic islet cell line.

“…In all systems, the response to BBS is rapid and transient. Infusion of BBS in dogs and humans produced a maximal stimulation of insulin secretion within 5 to 15 min followed by a decrease in insulin levels during continued infusion of the peptide (11)(12)(13)(14). Similarly, in perfused isolated canine pancreas, stimulation of insulin release was maximal after 2 min and decreased thereafter (15,16).…”

“…Both in vivo and in perfused pancreas the stimulatory effect of BBS on insulin secretion is transient (11)(12)(13)(14)(15)(16). Similarly, in HIT cells the time course for BBS-stimulated insulin secretion shows a return to the basal secretory rate by 90 min in the continued presence of the peptide.…”

“…BBS is a potent stimulator of insulin secretion when infused intravenously into either humans or experimental animals (10)(11)(12)(13)(14). In addition, BBS-like peptides are present in peptidergic neurons of the mammalian pancreas, and electrical stimulation of the splanchnic nerve has been shown to increase BBS levels in peripheral plasma to concentrations sufficient to stimulate insulin release (29,30).…”

“…Intravenous infusion of BBS in humans and dogs causes an increase in the plasma concentrations of both insulin and glucagon and lowers blood glucose levels (10)(11)(12)(13)(14). In vitro, BBS stimulates the secretion of insulin and glucagon by perfused dog pancreas (15,16), whereas it has been shown to either stimulate (17) or inhibit insulin release by isolated rat pancreas (18 (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27), cholecystokinin octapeptide, oxytocin, vasopressin, growth-hormone releasing factor(1-44), secretin, and vasoactive intestinal peptide were purchased from Peninsula Laboratories (San Carlos, CA).…”