Receptors for glucagon-like peptide-1(7-36) amide on rat insulinoma-derived cells

Specific binding of ¹²⁵I-labelled glucagon-like peptide-1(7-36)amide (GLP-1(7-36)amide) to rat insulinoma derived RINm5F cells was dependent upon time and temperature and was proportional to cell concentration. Binding of radioactivity was inhibited in a concentration-dependent manner by GLP-1(17-36) amide consistent with the presence of a single class of binding site with a dissociation constant (K(d)) of 204 ± 8 pmol/l (mean ± S.E.M.). Binding of the peptide resulted in a dose-dependent increase in cyclic AMP concentrations (half maximal response at 250 ± 20 pmol/l). GLP-1(1-36)amide was approximately 200 times less potent than GLP-1(7-36)amide in inhibiting the binding of ¹²⁵I-labelled GLP-1(7-36)amide to the cells (K(d) of 45 ± 6 nmol/l). Binding sites for GLP-1 (7-36)amide were not present on dispersed enterocytes from porcine small intestine.