title: Double disruption of α2A- and α2C-adrenoceptors induces endothelial dysfunction in mouse small arteries: role of nitric oxide synthase uncoupling.
abstract: Knockout mice lacking both α2A- and α2C-adrenergic receptors (α2A/α2C-ARKO) provide a model for understanding the mechanisms underlying the deleterious effects of sympathetic hyperactivity on the cardiovascular system. Thus, in the present study we investigated the vascular reactivity of large and small arteries of α2A/α2C-ARKO mice. Aorta and mesenteric small arteries (MSAs) from 7-month-old male α2A/α2C-ARKO mice and congenic C57BL6/J mice (wild-type, WT) were studied. In the aorta, noradrenaline- and serotonin-induced contraction was similar between groups, but in MSAs there was an increase in agonist-induced contraction in α2A/α2C-ARKO compared with WT. The l-NAME effect was reduced in MSAs of α2A/α2C-ARKO mice compared with WT mice, as was basal NO evaluated by a 4,5-diaminofluorescein diacetate probe. Increased total endothelial nitric oxide synthase (eNOS) protein expression was observed in MSAs from α2A/α2C-ARKO mice, while the dimer/monomer ratio of eNOS was decreased. Mesenteric small arteries from α2A/α2C-ARKO mice showed an increase in ethidium bromide-positive nuclei, indicating oxidative stress, which was attenuated by incubation with l-NAME. The sympathetic hyperactivity present in α2A/α2C-ARKO mice alters vascular reactivity only in certain types of arteries. Moreover, after chronic sympathetic hyperactivity, uncoupling eNOS may be a significant source of superoxide anion and reduced NO bioavailability in small vessels, increasing the contractile tone.
authors.affiliation: Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil.
authors.forename: Gisele K
authors.initials: GK
authors.lastname: Couto
authors.affiliation: Department of Structural and Functional Biology, Institute of Biology, State University of Campinas, Campinas, SP, Brazil.
authors.forename: Ana P
authors.initials: AP
authors.lastname: Davel
authors.affiliation: School of Physical Education and Sport, University of São Paulo, São Paulo, SP, Brazil.
authors.forename: Patrícia C
authors.initials: PC
authors.lastname: Brum
authors.affiliation: Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil lrossoni@icb.usp.br.
authors.forename: Luciana V
authors.initials: LV
authors.lastname: Rossoni
mesh_terms: D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018341:Receptors, Adrenergic, alpha-2 / Q000235:genetics / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D018341:Receptors, Adrenergic, alpha-2; D052250:Nitric Oxide Synthase Type III; D019331:NG-Nitroarginine Methyl Ester