title: Role of oxidative stress and nitric oxide in regulation of spontaneous tone in aorta of DOCA-salt hypertensive rats.
abstract: 1. The roles of nitric oxide (NO), superoxide anion (O(2)(-)), and hydrogen peroxide (H(2)O(2)) in the modulation of spontaneous tone were investigated in isolated aorta from deoxycorticosterone acetate (DOCA)-salt hypertensive rats. 2. Increases in preload from 1 to 5 g were accompanied by increases in spontaneous tone in aortic rings from DOCA-salt hypertensive rats but not from SHAM-normotensive rats. 3. Tone was higher in endothelium-denuded aortic rings than in endothelium-intact vessels. Inhibition of nitric oxide synthase (NOS) with 300 microM N(G)-nitro-L-arginine methyl ester (l-NAME) increased spontaneous tone. 4. Basal O(2)(-) generation was higher in aortic rings from DOCA-salt hypertensive rats than in those from SHAM-normotensive rats. Stretch increased O(2)(-) levels even further in the DOCA-salt group. In rings isolated from DOCA-salt hypertensive rats, administration of the O(2)(-) scavenger, superoxide dismutase (SOD, 150 U ml(-1)), or the nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase inhibitor, apocynin (100 microM), completely abolished the development of spontaneous tone in endothelium-intact aortic rings but not in endothelium-denuded or in L-NAME-treated rings. SOD and apocynin decreased the generation of O(2)(-) in endothelium-intact, endothelium-denuded, and L-NAME-treated aortic rings. 5. Oral treatment of DOCA-salt hypertensive rats with the O(2)(-) scavengers, tempol or tiron, or with apocynin for 3 weeks prevented the development of hypertension and abolished the increases in O(2)(-) generation and spontaneous tone. 6. Administration of catalase (1000 U ml(-1)) to aortic rings increased spontaneous tone in vessels from DOCA-salt hypertensive rats. 7. Administration of the cyclooxygenase (COX) inhibitor, valeroyl salicylate, or the thromboxane/prostaglandin antagonist, SQ 29548, to aortic rings abolished tone. 8. The results suggest that NO plays a major role in preventing the generation of spontaneous tone in isolated aortic rings from DOCA-salt hypertensive rats. NADPH-oxidase-derived O(2)(-) enhanced spontaneous tone by inactivating NO. Endogenous H(2)O(2) appears to mitigate the increase in tone. In addition, a COX component may also contribute to spontaneous tone.
authors.affiliation: Department of Pharmacology and the Cardiovascular Risk Factor Reduction Unit, College of Medicine, University of Saskatchewan, Saskatoon, SK, Canada S7N 5E5.
authors.forename: Mahua
authors.initials: M
authors.lastname: Ghosh
authors.forename: Hui Di
authors.initials: HD
authors.lastname: Wang
authors.forename: J Robert
authors.initials: JR
authors.lastname: McNeill
mesh_terms: D000166:Acridines / Q000378:metabolism; D000818:Animals; D001013:Aorta, Thoracic / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D015153:Blotting, Western; D002118:Calcium / Q000502:physiology; D002374:Catalase / Q000494:pharmacology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D003900:Desoxycorticosterone; D004730:Endothelium, Vascular / Q000502:physiology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006973:Hypertension / Q000139:chemically induced / Q000503:physiopathology*; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008163:Luminescent Measurements; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009129:Muscle Tonus / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III; D009842:Oligopeptides / Q000494:pharmacology; D018384:Oxidative Stress / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism; D010456:Peptides, Cyclic / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017482:Receptors, Thromboxane / Q000037:antagonists & inhibitors; D013481:Superoxides / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors
chemical_list: D000166:Acridines; D016861:Cyclooxygenase Inhibitors; D009842:Oligopeptides; D010456:Peptides, Cyclic; D010880:Piperidines; D017482:Receptors, Thromboxane; D013481:Superoxides; C033472:10,10'-dimethyl-9,9'-biacridinium; D009569:Nitric Oxide; C002744:3-nitrotyrosine; D003900:Desoxycorticosterone; D014443:Tyrosine; C086539:BQ 788; D006861:Hydrogen Peroxide; D002374:Catalase; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D014969:Xanthine Oxidase; C072247:cyclo(Trp-Asp-Pro-Val-Leu); D010100:Oxygen; D002118:Calcium