We have found [125I]glucagon-like peptide (GLP)-1(7–36)amide specific binding activity in rat liver and isolated hepatocyte plasma membranes, with an Mr of approximately 63 000, estimated by cross-linking and SDS-PAGE. The specific binding was time- and membrane protein concentration-dependent, and equally displaced by unlabelled GLP-1(7–36)amide and by GLP-1(1–36)amide, achieving its ID50 at 3×10−9 m of the peptides. GLP-1(7–36)amide did not modify the basal or the glucagon (10−8 m)-stimulated adenylate cyclase in the hepatocyte plasma membranes. These data, together with our previous findings of a potent glycogenic effect of GLP-1(7–36)amide in isolated rat hepatocytes, led us to postulate that the insulin-like effects of this peptide on glucose liver metabolism could be mediated by a type of receptor probably different from that described for GLP-1 in pancreatic B-cells or, alternatively, by the same receptor which, in this tissue as well as in muscle, uses a different transduction system.
Journal of Endocrinology (1995) 146, 183–189