Journal
CANADIAN JOURNAL OF PHYSIOLOGY AND PHARMACOLOGY
Volume 96, Issue 8, Pages 719-727Publisher
CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS
DOI: 10.1139/cjpp-2017-0477
Keywords
vascular; inducible nitric oxide synthase; hypertension; SHRSP
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Funding
- Fundacao de Amparo a Pesquisa do Estado de Mato Grosso (FAPEMAT) [151371/2014]
- Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES) [23038009165/2013-48]
- Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [2010/52214-6]
- Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) [471675/2013-0, 305823/2015-9, 445777/2014-1]
- National Heart, Lung and Blood Institute at the National Institutes of Health [5R01HL071138-08]
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The endothelium is crucial for the maintenance of vascular tone by releasing several vasoactive substances, including nitric oxide (NO). Systemic mean arterial pressure is primarily regulated by the resistance vasculature, which has been shown to exhibit increased vascular reactivity, and decreased vasorelaxation during hypertension. Here, we aimed to determine the mechanism for mesenteric artery vasorelaxation of the stroke-prone spontaneously hypertensive rat (SHRSP). We hypothesized that endothelial NO synthase (eNOS) is upregulated in SHRSP vessels, increasing NO production to compensate for the endothelial dysfunction. Concentration-response curves to acetylcholine (ACh) were performed in second-order mesenteric arteries; we observed decreased relaxation responses to ACh (maximum effect elicited by the agonist) as compared with Wistar-Kyoto (WKY) controls. Vessels from SHRSP incubated with N omega-nitro-L-arginine methyl ester and (or) indomethacin exhibited decreased ACh-mediated relaxation, suggesting a primary role for NO-dependent relaxation. Vessels from SHRSP exhibited a significantly decreased relaxation response with inducible NO synthase (iNOS) inhibition, as compared with WKY vessels. Western blot analysis showed increased total phosphorylated NF-kappa B, and phosphorylated and total eNOS in SHRSP vessels. Overall, these data suggest a compensatory role for NO by increased eNOS activation. Moreover, we believe that iNOS, although increasing NO bioavailability to compensate for decreased relaxation, leads to a cycle of further endothelial dysfunction in SHRSP mesenteric arteries.
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