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(Hypertension. 2005;46:1355.)
© 2005 American Heart Association, Inc.
Original Articles |
From the Hypertension and Vascular Research Division (Y.S., O.A.C., J.X., N.-E.R., F.W., C.L., P.J.P., X.-P.Y.), Department of Internal Medicine, and the Department of Biostatistics and Research Epidemiology (J.J.Y.), Henry Ford Health System and Wayne State University Detroit, Michigan.
Correspondence to Xiao-Ping Yang, MD, FAHA, Senior Staff Investigator, Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Health System, and Associate Professor, Wayne State University, 2799 W Grand Blvd, Detroit, MI 48202-2689. E-mail xpyang1{at}hfhs.org
Although NO derived from endothelial NO synthase (eNOS) is thought to be cardioprotective, the role of inducible NO synthase (iNOS) remains controversial. Using mice lacking iNOS (iNOS/), we studied (1) whether development of hypertension, cardiac hypertrophy, and dysfunction after deoxycorticosterone acetate (DOCA)salt would be less severe compared with wild-type controls (WT; C57BL/6J), and (2) whether the cardioprotection attributable to lack of iNOS is mediated by reduced oxidative stress. Mice were uninephrectomized and received either DOCA-salt (30 mg/mouse SC and 1% NaCl+0.2% KCl in drinking water) or vehicle (tap water) for 12 weeks. Systolic blood pressure (SBP) was measured weekly. Left ventricular (LV) ejection fraction (EF) by echocardiography and cardiac response to isoproterenol (50 ng/mouse IV) were studied at the end of the experiment. Expression of eNOS and iNOS as well as the oxidative stress markers 4-hydroxy-2-nonenal (4-HNE, a marker of lipid peroxidation) and nitrotyrosine (a marker for peroxynitrite) were determined by Western blot and immunohistochemical staining, respectively. DOCA-salt increased SBP and LV weight similarly in both strains and decreased EF in WT but not in iNOS/. Cardiac contractile and relaxation responses to isoproterenol were greater, 4-HNE and nitrotyrosine levels were lower, and eNOS expression tended to be higher in iNOS/. We conclude that lack of iNOS leads to better preservation of cardiac function, which may be mediated by reduced oxidative stress and increased eNOS; however, it does not seem to play a significant role in preventing DOCA-saltinduced hypertension and hypertrophy.
Key Words: nitric oxide synthase cardiac function oxidative stress
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