Nitric oxide modulates cardiac contractility and oxygen consumption without changing contractile efficiency.
Nitric oxide (NO) affects myocardial contractility and myocardial oxygen consumption (MVO2) in vitro. In alpha-chloralose-anesthetized dogs instrumented for the measurements of left ventricular (LV) pressure, LV volume using a conductance catheter, coronary blood flow, and coronary venous oxygen saturation (ScvO2) using a fiber-optic catheter, LV end-systolic pressure-volume relationships (ESPVR) and the relationship between MVO2 and LV pressure-volume area (PVA) were analyzed before and after intravenous infusions of the NO synthase inhibitor NG-monomethyl-L-arginine acetate (L-NMMA; 5 mg/kg, 8 dogs) and the NO substrate L-arginine (600 mg/kg, 7 dogs). L-NMMA increased the slope of the ESPVR (Emax) (P < 0.05) without changing contractile efficiency indicated by the inverse of the slope of the MVO2-PVA line. L-NMMA also increased unloaded MVO2, indicated by the y-axis intercept of the MVO2-PVA line (P < 0.05). In contrast, L-arginine decreased Emax (P < 0.05) while decreasing MVO2 (P < 0.05), and without changing contractile efficiency. The basal oxygen metabolism was not affected by L-NMMA and L-arginine. These data imply that endogenous NO spares MVO2 by reducing oxygen use in excitation-contraction coupling and attenuates cardiac contractility without changing contractile efficiency.
Second Department of Internal Medicine, Hirosaki University School of Medicine, Hirosaki University, Hirosaki 036, Japan.
N
N
Suto
A
A
Mikuniya
T
T
Okubo
H
H
Hanada
N
N
Shinozaki
K
K
Okumura
D000818:Animals; D001120:Arginine / Q000494:pharmacology; D001794:Blood Pressure; D003326:Coronary Circulation / Q000187:drug effects / Q000502:physiology; D004285:Dogs; D004562:Electrocardiography; D005336:Fiber Optic Technology; D006321:Heart / Q000502:physiology*; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism*; D009569:Nitric Oxide / Q000502:physiology*; D009638:Norepinephrine / Q000097:blood; D055100:Optical Fibers; D010092:Oximetry / Q000295:instrumentation / Q000379:methods; D010101:Oxygen Consumption / Q000187:drug effects; D015203:Reproducibility of Results; D013599:Systole; D016277:Ventricular Function, Left / Q000502:physiology*; D019323:omega-N-Methylarginine / Q000494:pharmacology*
D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine; D009638:Norepinephrine