Effects of neuromedin B and neuromedin C on exocrine and endocrine rat pancreas.
Neuromedin B and neuromedin C are novel decapeptides that have recently been isolated from porcine spinal cord and canine intestinal mucosa and show striking sequence homology with bombesin and gastrin-releasing peptide (GRP-27) at the carboxyl-terminal region. The effects of synthetic neuromedin B and C on exocrine pancreatic function and insulin release have been compared with bombesin and GRP-27 in isolated pancreatic acini and isolated perfused pancreas in rat. Neuromedin B and C as well as bombesin and GRP-27 were able to cause stimulation of amylase release. The relative efficacy of neuromedin B, C, bombesin, and GRP-27 was the same as that of cholecystokinin octapeptide (CCK-8). Bombesin and GRP-27 were equipotent, and both were approximately 15-fold less potent than CCK-8. Neuromedin C was approximately 2-fold more potent, whereas neuromedin B as approximately 10-fold less potent than bombesin and GRP-27. All of these peptides stimulated insulin release that was limited to the first 3 min of a 20-min perfusion. However, GRP-27 and its related peptides were weak stimulants of insulin release compared with their abilities to stimulate exocrine pancreatic secretion. Bombesin and neuromedin B id not stimulate insulin release at doses stimulating pancreatic exocrine secretion. Neuromedin B was also approximately 10-fold less potent than neuromedin C, bombesin, and GRP-27 in eliciting insulin secretion. Because bombesin-like immunoreactivity is found to be present in nerves in the pancreas, neuromedin B and C may be neurotransmitters or neuromodulators and exert a direct local neurocrine action on enzyme secretion by acinar cells and insulin secretion by the islets.
D000681:Amylases / Q000378:metabolism; D000818:Animals; D001839:Bombesin / Q000494:pharmacology*; D019886:Gastrin-Releasing Peptide; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D015287:Neurokinin B / Q000031:analogs & derivatives*; D009479:Neuropeptides / Q000494:pharmacology*; D010179:Pancreas / Q000187:drug effects*; D010189:Pancreatic Juice / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D012636:Secretory Rate / Q000187:drug effects; D012844:Sincalide / Q000494:pharmacology
D007328:Insulin; D009479:Neuropeptides; D010446:Peptide Fragments; D010455:Peptides; D019886:Gastrin-Releasing Peptide; C040794:neuromedin C; D015287:Neurokinin B; C038393:neuromedin B; D000681:Amylases; D012844:Sincalide; D001839:Bombesin