title: Glucagon antagonists. Synthesis and inhibitory properties of Asp3-containing glucagon analogs.
abstract: In an effort to find analogs of glucagon that would bind to the glucagon receptor of the rat liver membrane but would not activate membrane-bound adenyl cyclase, several hybrid molecules were synthesized which contained sequences from both glucagon and secretin. [Asp3, Glu9]Glucagon and [Asp3, Glu9, Arg12]glucagon were inactive in the adenyl cyclase assay even at high concentrations but retained some binding affinity for the receptor. They were able to displace 125I-glucagon completely from its receptor and could completely inhibit the activation of adenyl cyclase by natural or synthetic glucagon. The inhibition index [I/A]50 was approximately 110 for both analogs. [Asp3]Glucagon, [Glu3]glucagon and [Asp3, Lys17, 18, Glu21]glucagon were weak partial agonists, while [Asp3, Glu21]glucagon was inactive and a poor inhibitor. The peptides were synthesized by solid-phase methods and purified to homogeneity by reverse-phase high-performance liquid chromatography on C18 silica columns. These are the first fully synthetic competitive glucagon antagonists to be reported.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001224:Aspartic Acid; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005934:Glucagon / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors* / Q000138:chemical synthesis / Q000494:pharmacology; D008099:Liver / Q000378:metabolism; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011964:Receptors, Gastrointestinal Hormone / Q000378:metabolism; D018027:Receptors, Glucagon; D012633:Secretin / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology
chemical_list: D011964:Receptors, Gastrointestinal Hormone; D018027:Receptors, Glucagon; D012633:Secretin; D001224:Aspartic Acid; D005934:Glucagon; D000262:Adenylyl Cyclases