Endogenous endothelial nitric oxide synthase-derived nitric oxide is a physiological regulator of myocardial oxygen consumption.
Our objective was to determine the precise role of endothelial nitric oxide synthase (eNOS) as a modulator of cardiac O2 consumption and to further examine the role of nitric oxide (NO) in the control of mitochondrial respiration. Left ventricle O2 consumption in mice with defects in the expression of eNOS [eNOS (-/-)] and inducible NOS [iNOS (-/-)] was measured with a Clark-type O2 electrode. The rate of decreases in O2 concentration was expressed as a percentage of the baseline. Baseline O2 consumption was not significantly different between groups of mice. Bradykinin (10(-4) mol/L) induced significant decreases in O2 consumption in tissues taken from iNOS (-/-) (-28+/-4%), wild-type eNOS (+/+) (-22+/-4%), and heterozygous eNOS(+/-) (-22+/-5%) but not homozygous eNOS (-/-) (-3+/-4%) mice. Responses to bradykinin in iNOS (-/-) and both wild-type and heterozygous eNOS mice were attenuated after NOS blockade with N-nitro-L-arginine methyl ester (L-NAME) (-2+/-5%, -3+/-2%, and -6+/-5%, respectively, P<0.05). In contrast, S-nitroso-N-acetyl-penicillamine (SNAP, 10(-4) mol/L), which releases NO spontaneously, induced decreases in myocardial O2 consumption in all groups of mice, and such responses were not affected by L-NAME. In addition, pretreatment with bacterial endotoxin elicited a reduction in basal O2 consumption in tissues taken from normal but not iNOS (-/-)-deficient mice. Our results indicate that the pivotal role of eNOS in the control of myocardial O2 consumption and modulation of mitochondrial respiration by NO may have an important role in pathological conditions such as endotoxemia in which the production of NO is altered.
Loke
K E
KE
Departments of Physiology and Pathology, New York Medical College, Valhalla, NY, USA.
McConnell
P I
PI
Tuzman
J M
JM
Shesely
E G
EG
Smith
C J
CJ
Stackpole
C J
CJ
Thompson
C I
CI
Kaley
G
G
Wolin
M S
MS
Hintze
T H
TH
D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009206:Myocardium / Q000201:enzymology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000235:genetics*; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D010101:Oxygen Consumption / Q000502:physiology; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology
D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; C110881:S-nitro-N-acetylpenicillamine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496317:Nos2 protein, mouse; C496315:Nos3 protein, mouse; D010396:Penicillamine; D001920:Bradykinin; D019331:NG-Nitroarginine Methyl Ester