Specific binding sites for 125I-labelled rat peptide-histidine-isoleucine (PHI) were identified on rat insulinoma-derived RINm5F cells. The concentrations of peptides producing half-maximal displacement of label were rat PHI, 0.36 ± 0.14 nM, vasoactive intestinal polypeptide (VIP), 0.38 ± 0.13 nM and secretin, approximately 0.2 μM. Glucagon and glucagon-like peptide-1(7-36)amide were without effect on binding. PHI and VIP produced dose-dependent increases in cAMP production in the cells that were significantly (P < 0.05) above unstimulated rates for ligand concentrations between 10-8 and 10 -6 M. Both PHI and VIP produced a small but significant (P < 0.05) enhancement in the rate of release of immunoreactive insulin from the cells but the effect was not dose dependent.
- Cyclic AMP
- Insulin release
- Vasoactive intestinal polypeptide
ASJC Scopus subject areas
- Molecular Biology