title: Conversion of adrenergic mechanism from an alpha- to a beta-type during primary culture of rat hepatocytes. Accompanying decreases in the function of the inhibitory guanine nucleotide regulatory component of adenylate cyclase identified as the substrate of islet-activating protein.
abstract: Adrenergic mechanism for phosphorylase activation was gradually converted from an alpha 1- to a beta 2-type during primary culture of rat hepatocytes. beta 2-Receptor-mediated cAMP generation was also much greater in 8-h cultured cells than in fresh cells. Incubation of hepatocyte membranes with [alpha-32P]NAD and the preactivated A-protomer (an active component) of islet-activating protein (IAP), pertussis toxin, resulted in the ADP-ribosylation of a specific IAP substrate protein (Mr = 41,000). This ADP-ribosylation diminished progressively when the membrane-donor hepatocytes had been cultured. The early diminution was interfered with by the addition of nicotinamide or isonicotinamide, a potent inhibitor of ADP-ribosyltransferase, to the culture medium. The decrease of the IAP substrate was well correlated with the potentiation of beta-adrenergic functions under various conditions of culture. beta-Receptor-mediated activation of GTP-dependent membrane adenylate cyclase was, but glucagon-induced activation was not enhanced by either prior culture of hepatocytes or prior exposure of membranes to the A-protomer of IAP. There was no further enhancement, however, when membranes from cultured cells were exposed to the active toxin. Thus, the IAP-susceptible inhibitory guanine nucleotide-regulatory protein is coupled to beta-adrenergic receptors in such a manner as to reduce the degree of activation of cyclase, and the decrease in this IAP substrate may be responsible, at least partly, for development of beta-receptor functions during culture of hepatocytes. Its possible relation to accompanying inhibition of alpha 1-receptor functions is discussed.
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D037361:Adenylate Cyclase Toxin; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006728:Hormones / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D037342:Pertussis Toxin; D006005:Phosphorylases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D010566:Virulence Factors, Bordetella
chemical_list: D037361:Adenylate Cyclase Toxin; D001427:Bacterial Toxins; D006728:Hormones; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D000242:Cyclic AMP; D006005:Phosphorylases; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D007545:Isoproterenol