Bombesin, a peptide with widespread biological actions, has been demonstrated in human
tissues by immunological methods. To investigate its effect in man, synthetic bombesin
was infused at low doses in six male volunteers. Bombesin at 2.4 pmol kg-1 min-1 produced
significant rises in plasma insulin, glucagon, pancreatic polypeptide, gastrin, cholecystokinin,
motilin, glucose-dependent insulinotropic polypeptide, neurotensin, enteroglucagon,
vasoactive intestinal polypeptide, and serum calcium. In contrast, bombesin caused
a profound fall in parathyroid hormone levels and reduced plasma glucose concentrations.
A late rise in plasma calcitonin was also observed. Bombesin had no significant effect
on the pituitary hormones, TSH, GH, PRL, or cortisol. No hormonal changes or alterations
in calcium were noted during saline infusions. Bombesin has a marked stimulatory effect
on gastrointestinal hormones, which is unique and opposite to the effect of somatostatin,
a potent inhibitor of gut hormone release. Bombesin also influences calcium-regulating
hormones, either directly or through its action on gut hormones. The bombesin concentrations
achieved with the dosages used were low enough to indicate a possible physiological
role for the endogenous peptide.