Bombesin-like immunoreactivity in the pancreas of man and other mammalian species.

Bombesin-like immunoreactivity has been measured in pancreatic tissues of man (12.4 +/- 1.2 pmol/g), pig (15.8 +/- 3.2), calf (4.3 +/- 0.9), rat (8.5 +/- 1.2) and guinea-pig (2.8 +/- 0.6) by a specific radioimmunoassay. Gel filtration of the pancreatic extracts revealed 2 major immunoreactive peaks: the earlier peak was eluted in the position of porcine gastrin-releasing peptide, and the later peak was eluted just after the amphibian bombesin standard. Immunocytochemistry demonstrated the presence of bombesin-like immunoreactivity in nerves in the rat pancreas, particularly in the exocrine pancreas, and occasionally in the peri-insular spaces. Isolated rat pancreatic islets were found to contain small quantities of bombesin-like immunoreactivity (0.037 +/- 0.003 fmol/islet) suggesting that mammalian bombesin-like peptides may be involved in the regulation of endocrine as well as exocrine pancreatic secretion.