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1Department of Physiology, New York Medical College, Valhalla, New York 10595; 2Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, Louisiana 71130-3932; and 3Department of Cell Biology and Genetics and 4Department of Vascular Surgery, Erasmus University Medical Center, Rotterdam 3000 DR, The Netherlands
Submitted 16 March 2004 ; accepted in final form 13 July 2004
Our objective was to investigate the potential role of selective endothelial nitric oxide (NO) synthase (eNOS) overexpression in coronary blood vessels in the control of myocardial oxygen consumption (MVO2). Transgenic (Tg) eNOS-overexpressing mice (eNOS Tg) (n = 22) and wild-type (WT) mice (n = 24) were studied. Western blot analysis indicated greater than sixfold increase of eNOS in cardiac tissue. Echocardiography in awake mice indicated no difference in cardiac function between WT and eNOS Tg; however, systolic pressure in eNOS Tg mice decreased significantly (126 ± 2.3 to 109 ± 2.3 mmHg; P < 0.05), whereas heart rate (HR) was not different. Total peripheral resistance (TPR) was also decreased (9.8 ± 0.8 to 7.6 ± 0.4 4 mmHg·ml1·min; P < 0.05) in eNOS Tg. Furthermore, female eNOS Tg mice showed even lower TPR (7.2 ± 0.4 mmHg·ml1·min) compared with male eNOS mice (8.6 ± 0.5, mmHg·ml·min1; P < 0.05). Left ventricular slices were isolated from WT and eNOS Tg mice. With the use of a Clark-type oxygen electrode in an airtight bath, MVO2 was determined as the percent decrease during increasing doses (1010 to 104 mol/l) of bradykinin (BK), carbachol (CCh), forskolin (1012 to 106 mol/l), or S-nitroso-N-acetyl penicillamine (SNAP; 107 to 104 mol/l). Baseline MVO2 was not different between WT (181 ± 13 nmol·g1·min1) and eNOS Tg (188 ± 14 nmol·g1·min1). BK decreased MVO2 (104 mol/l) in WT by 17% ± 1.1 and 33% ± 2.7 in eNOS Tg (P < 0.05). CCh also decreased MVO2, 104 mol/l, in WT by 20% ± 1.7 and 31% ± 2.0 in eNOS Tg (P < 0.05). Forskolin (106 mol/l) or SNAP (104 mol/l) also decreased MVO2 in WT by 24% ± 2.8 and 36% ± 1.8 versus eNOS 31% ± 1.8 and 37% ± 3.5, respectively. N-nitro-L-arginine methyl ester (103 mol/l) inhibited the MVO2 reduction to BK, CCh, and forskolin by a similar degree (P < 0.05), but not to SNAP. Thus selective overexpression of eNOS in cardiac blood vessels in mice enhances the control of MVO2 by eNOS-derived NO.
forskolin; nitric oxide
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