title: Impaired endothelial function and microvascular asymmetrical dimethylarginine in angiotensin II-infused rats: effects of tempol.
abstract: Angiotensin (Ang) II causes endothelial dysfunction, which is associated with cardiovascular risk. We investigated the hypothesis that Ang II increases microvascular reactive oxygen species and asymmetrical dimethylarginine and switches endothelial function from vasodilator to vasoconstrictor pathways. Acetylcholine-induced endothelium-dependent responses of mesenteric resistance arterioles were assessed in a myograph and vascular NO and reactive oxygen species by fluorescent probes in groups (n=6) of male rats infused for 14 days with Ang II (200 ng/kg per minute) or given a sham infusion. Additional groups of Ang or sham-infused rats were given oral Tempol (2 mmol · L(-1)). Ang II infusion increased mean blood pressure (119±5 versus 89±7 mm Hg; P<0.005) and plasma malondialdehyde (0.57±0.02 versus 0.37±0.05 μmol · L(-1); P<0.035) and decreased maximal endothelium-dependent relaxation (18±5% versus 54±6%; P<0.005) and hyperpolarizing (19±3% versus 29±3%; P<0.05) responses and NO activity (0.9±0.1 versus 1.6±0.2 U; P<0.01) yet enhanced endothelium-dependent contraction responses (23±5% versus 5±5%; P<0.05) and reactive oxygen species production (0.82±0.05 versus 0.15±0.03 U; P<0.01). Ang II decreased the expression of dimethylarginine dimethylaminohydrolase 2 and increased asymmetrical dimethylarginine in vessels (450±50 versus 260±35 pmol/mg of protein; P<0.01) but not plasma. Tempol prevented any significant changes with Ang II. In conclusion, Ang redirected endothelial responses from relaxation to contraction, reduced vascular NO, and increased asymmetrical dimethylarginine. These effects were dependent on reactive oxygen species and could, therefore, be targeted with effective antioxidant therapy.
authors.affiliation: Division of Nephrology and Hypertension, Georgetown University, Washington, DC, USA.
authors.forename: Dan
authors.initials: D
authors.lastname: Wang
authors.forename: Zaiming
authors.initials: Z
authors.lastname: Luo
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Wang
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Jose
authors.forename: John R
authors.initials: JR
authors.lastname: Falck
authors.forename: William J
authors.initials: WJ
authors.lastname: Welch
authors.forename: Shakil
authors.initials: S
authors.lastname: Aslam
authors.forename: Tom
authors.initials: T
authors.lastname: Teerlink
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Wilcox
mesh_terms: D000704:Analysis of Variance; D000804:Angiotensin II / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001120:Arginine / Q000031:analogs & derivatives* / Q000378:metabolism; D001160:Arterioles / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D003497:Cyclic N-Oxides / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D008315:Malondialdehyde / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D013113:Spin Labels; D014662:Vasoconstrictor Agents / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D003497:Cyclic N-Oxides; D017382:Reactive Oxygen Species; D013113:Spin Labels; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D008315:Malondialdehyde; C018524:N,N-dimethylarginine; D001120:Arginine; C001803:tempol