Stimulation of dog gastropancreatic hormone release by neuromedin B and its analogues.

The effects on gastrin, insulin, and glucagon release of neuromedin B (NMB), the C-fragment decapeptide of gastrin-releasing peptide-10 (GRP-10), seven analogues replacing amino acid positions 3, 6, and 9, and two C-terminal desamide analogues were examined in conscious dogs using intravenous bolus injection of these peptides study the structure-activity relationship of two bombesin-related peptides identified in mammals. The replacement from valine of position 6 of GRP-10 to threonine effectively reduced the stimulatory potency of these hormone secretions. Removal of the C-terminal amide of NMB and GRP-10 resulted in an almost complete loss of their stimulatory effect on gastrin secretion. [Leu3]GRP-10 elicited the most potent stimulatory activity on three hormone secretions among the analogues including NMB and GRP-10. These results indicate that valine in position 6 of GRP-10 and C-terminal amide of two peptides play an important role in the bioactivities of bombesin family peptides.