title: Upregulation of beta-adrenergic receptors in heart failure due to volume overload.
abstract: To examine the mechanisms of changes in beta-adrenergic signal transduction in heart failing due to volume overload, we studied the status of beta-adrenoceptors (beta-ARs), G protein-coupled receptor kinase (GRK), and beta-arrestin in heart failure due to aortocaval shunt (AVS). Heart failure in rats was induced by creating AVS for 16 wk, and beta-AR binding, GRK activity, as well as their protein content, and mRNA levels were determined in both left and right ventricles. The density and protein content for beta1-ARs, unlike those for beta2-ARs, were increased in the failing hearts. Furthermore, protein contents for GRK isoforms and beta-arrestin-1 were decreased in membranous fractions and increased in cytosolic fractions from the failing hearts. On the other hand, steady-state mRNA levels for beta1-ARs and GRK2, as well as protein content for Gbetagamma-subunits, did not change in the failing heart. Basal cardiac function was depressed; however, both in vivo and ex vivo positive inotropic responses of the failing hearts to isoproterenol were augmented. Treatment of AVS animals with imidapril (1 mg.kg(-1).day(-1)) or losartan (20 mg.kg(-1).day(-1)) retarded the progression of heart failure; partially prevented changes in beta1-ARs, GRKs, and beta-arrestin-1 in the failing myocardium; and attenuated the increase in positive inotropic effect of isoproterenol. These results indicate that upregulation of beta1-ARs is associated with subcellular redistribution of GRKs and beta-arrestin-1 in the failing heart due to volume overload. Furthermore, attenuation of alterations in beta-adrenergic system by imidapril or losartan may be due to blockade of the renin-angiotensin system in the AVS model of heart failure.
authors.affiliation: Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, 351 Tache Ave., Winnipeg, MB R2H 2A6, Canada.
authors.forename: Xi
authors.initials: X
authors.lastname: Wang
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Sentex
authors.forename: Harjot K
authors.initials: HK
authors.lastname: Saini
authors.forename: Donald
authors.initials: D
authors.lastname: Chapman
authors.forename: Naranjan S
authors.initials: NS
authors.lastname: Dhalla
mesh_terms: D000818:Animals; D019390:Arrestins / Q000378:metabolism; D001810:Blood Volume; D002316:Cardiotonic Agents / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D054774:G-Protein-Coupled Receptor Kinase 5; D044387:GTP-Binding Protein beta Subunits / Q000378:metabolism; D044388:GTP-Binding Protein gamma Subunits / Q000378:metabolism; D006333:Heart Failure / Q000209:etiology* / Q000378:metabolism* / Q000503:physiopathology; D006439:Hemodynamics; D007545:Isoproterenol / Q000494:pharmacology; D009206:Myocardium / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D014018:Tissue Distribution; D015854:Up-Regulation; D051552:beta-Adrenergic Receptor Kinases; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins
chemical_list: C000605256:Arrb1 protein, rat; D019390:Arrestins; D002316:Cardiotonic Agents; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D011943:Receptors, Adrenergic, beta; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D051552:beta-Adrenergic Receptor Kinases; D054774:G-Protein-Coupled Receptor Kinase 5; C517897:Grk5 protein, rat; D007545:Isoproterenol