Glucagon-like peptide-1 binding to rat skeletal muscle

We have found [ 125I]glucagon-like peptide-1(7–36)-amide-specific binding activity in rat skeletal muscle plasma membranes, with an estimated M r of 63,000 by cross-linking and SDS-PAGE. The specific binding was time and membrane protein concentration dependent, and displaceable by unlabeled GLP-1(7–36)-amide with an ID 50 of 3 × 10 −9 M of the peptide; GLP-1(1–36)-amide also competed, whereas glucagon and insulin did not. GLP-1(7–36)-amide did not modify the basal adenylate cyclase activity in skeletal muscle plasma membranes. These data, together with our previous finding of a potent glycogenic effect of GLP-1(7–36)-amide in rat soleus muscle, and also in isolated hepatocytes, which was not accompanied by a rise in the cell cyclic AMP content, lead us to believe that the insulin-like effects of this peptide on glucose metabolism in the muscle could be mediated by a type of receptor somehow different to that described for GLP-1 in pancreatic B cells, where GLP-1 action is mediated by the cyclic AMP-adenylate cyclase system.