title: beta(3)-adrenoceptor deficiency blocks nitric oxide-dependent inhibition of myocardial contractility.
abstract: The cardiac beta-adrenergic pathway potently stimulates myocardial performance, thereby providing a mechanism for myocardial contractile reserve. beta-Adrenergic activation also increases cardiac nitric oxide (NO) production, which attenuates positive inotropy, suggesting a possible negative feedback mechanism. Recently, in vitro studies suggest that stimulation of the beta(3)-adrenoceptor results in a negative inotropic effect through NO signaling. In this study, using mice with homozygous beta(3)-adrenoceptor deletion mutations, we tested the hypothesis that the beta(3)-adrenoceptor is responsible for beta-adrenergic activation of NO. Although resting indices of myocardial contraction were similar, beta-adrenergic-stimulated inotropy was increased in beta(3)(-/-) mice, and similar hyper-responsiveness was seen in mice lacking endothelial NO synthase (NOS3). NOS inhibition augmented isoproterenol-stimulated inotropy in wild-type (WT), but not in beta(3)(-/-) mice. Moreover, isoproterenol increased myocardial cGMP in WT, but not beta(3)(-/-), mice. NOS3 protein abundance was not changed in beta(3)(-/-) mice, and cardiac beta(3)-adrenoceptor mRNA was detected in both NOS3(-/-) and WT mice. These findings indicate that the beta(3)-adrenergic subtype participates in NO-mediated negative feedback over beta-adrenergic stimulation.
authors.affiliation: Department of Medicine, Cardiology Division, and. Department of Anesthesiology and Critical Care Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA.
authors.forename: P
authors.initials: P
authors.lastname: Varghese
authors.forename: R W
authors.initials: RW
authors.lastname: Harrison
authors.forename: R A
authors.initials: RA
authors.lastname: Lofthouse
authors.forename: D
authors.initials: D
authors.lastname: Georgakopoulos
authors.forename: D E
authors.initials: DE
authors.lastname: Berkowitz
authors.forename: J M
authors.initials: JM
authors.lastname: Hare
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D005246:Feedback; D007545:Isoproterenol / Q000494:pharmacology; D051379:Mice; D008817:Mice, Mutant Strains; D009200:Myocardial Contraction / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D011943:Receptors, Adrenergic, beta / Q000235:genetics / Q000378:metabolism*; D022702:Receptors, Adrenergic, beta-3; D013564:Sympathetic Nervous System / Q000502:physiology
chemical_list: D000318:Adrenergic beta-Agonists; D011943:Receptors, Adrenergic, beta; D022702:Receptors, Adrenergic, beta-3; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D007545:Isoproterenol