Characterization of receptors for glucagon-like peptide-1(7-36) amide on rat lung membranes

Abstract

Specific binding of 125I-labelled GLP-1(7-36)amide to rat lung membranes was dependent upon time and temperature and was proportional to membrane protein concentration. Binding was inhibited in a concentration-dependent manner by unlabelled GLP-l(7-36)amide consistent with the presence of a single class of binding sites with a dissociation constant (Kd) of 1.67 +/- 0.29 nmol/l. GLP-1(1-36)amide was 260 times less potent in inhibiting the binding of 125I-labelled GLP-1(7 36)amide to lung membranes (kd of 448 +/- 93 nmol/l). Vasoactive intestinal polypeptide and peptide-histidine-isolcucine also displaced 125I-labelled GLP-1(7-36)amide from the receptor concentration-dependently; the kd was 4.31 +/- 0.8 and 7.93 +/- 4.79 nmol/l. respectively. Guaninc nucleotides (GTP-[gamma]-S, GDP-[beta]-S) decreased the binding of 125I-labelled GLP-1(7-36)amide to rat lung membranes as was found for GLP-1(7-36)amide receptors in RINm5F cells which were also shown to be coupled to the adenylate cyclase system.