title: The glucagon receptor of rat liver plasma membrane can couple to adenylate cyclase without activating it.
abstract: 1. Activation of adenylate cyclase in rat liver plasma membranes by fluoride or GMP-P (NH)P yielded linear Arrheniun plots. Activation by glucagon alone, or in combination with either fluoride or GMP-P(NH)P resulted in biphasic Arrhenius plots with a well-defined break at 28.5 +/- 1 degrees C. 2. The competitive glucagon antagonist, des-His-glucagon did not activate the adenylate cyclase but produced biphasic Arrhenius plots in combination with fluoride or GMP-P(NH)P. The break temperatures and activation energies were very similar to those observed with glucagon alone, or in combination with either fluoride or GMP-P(NH)P. 3. It is concluded that although des-His-glucagon is a potent antagonist of glucagon, it nevertheless causes a structural coupling between the receptor and the catalytic unit.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D005459:Fluorides / Q000494:pharmacology; D005934:Glucagon / Q000378:metabolism* / Q000494:pharmacology; D006150:Guanine Nucleotides / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D011956:Receptors, Cell Surface; D013696:Temperature; D013816:Thermodynamics
chemical_list: D006150:Guanine Nucleotides; D011956:Receptors, Cell Surface; D005934:Glucagon; D000262:Adenylyl Cyclases; D005459:Fluorides