DETECTION OF THE HUMAN GLUCAGON-LIKE PEPTIDE 1(7-36) AMIDE RECEPTOR ON INSULINOMA-DERIVED CELL-MEMBRANES

I-125-glucagon-like peptide 1(7-36)amide was covalently cross-linked t o a specific binding protein in human insulinoma cell membranes. A sin gle radiolabeled band at M(r) 63,000 was identified by SDS-PAGE after solubilization of the ligand-binding protein complex. The molecular we ight of this apparent GLP-1 receptor in human endocrine pancreatic tis sue was of identical size as the GLP-1 receptor on rat insulinoma-deri ved RINmSF cell membranes. The radiolabeled band was undetectable when 1 mu M Of unlabeled GLP-1 (7-36)amide or of the GLP-1 antagonist exen din(9-39)amide was included in the binding assay. Utilizing isolated p oly-A+ RNA from the human insulinoma and a 1,500 bp Eco-RI fragment of the cDNA coding for the rat GLP-1(7-36)amide receptor for Northern bl ot analysis, a main hybridization signal at about 7 kb was found by No thern blotting. Our data provide the first direct evidence of the exis tence of GLP-1 receptors in human endocrine pancreatic tissue.