Importance of basal nitric oxide synthesis in regulation of myocardial blood flow.
OBJECTIVE
The aim was to investigate whether basal coronary vascular tone and myocardial perfusion depend upon endothelial nitric oxide (NO) synthesis.


METHODS
Myocardial blood flow and vascular resistance of the left and right ventricles were studied before and after intravenous infusions of either NG-nitro-L-arginine (L-NA), a specific inhibitor of NO synthase, or L-arginine, the precursor of NO synthesis. Radiolabelled microspheres were used to study myocardial blood flow in small tissue sections.


METHODS
14 anaesthetised male cats, weight 2.1-3.5 kg, were used.


RESULTS
Measurements were made before and 15 and 40 min after L-NA treatment (30 mg.kg-1 bolus followed by 1 mg.kg-1.min-1 infusion; n = 8), and before and 15 min after L-arginine treatment (30 mg.kg-1 bolus followed by 10 mg.kg-1.min-1 infusion; n = 6). L-NA significantly reduced coronary blood flow to the left and right ventricle, by 30(SEM 9) and 48(6)% respectively, after 15 min, but only to the right ventricle, by 45(8)%, after 40 min. Mean arterial pressure and myocardial vascular resistance were raised during the L-NA infusion. In contrast, L-arginine did not elicit any change in the variables studied.


CONCLUSIONS
The conductance of the coronary vascular bed and the resting myocardial blood flow is regulated by L-arginine derived nitric oxide, and exogenous L-arginine availability is not a limiting factor in this NO generation.
Benyó
Z
Z
Department of Neurology, University of Pennsylvania, Philadelphia 19104-6063.
Kiss
G
G
Szabó
C
C
Csáki
C
C
Kovách
A G
AG
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000502:physiology*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008863:Microspheres; D009569:Nitric Oxide / Q000378:metabolism*; D019335:Nitroarginine; D014655:Vascular Resistance / Q000187:drug effects
D019335:Nitroarginine; D009569:Nitric Oxide; D001120:Arginine