Does inhibition of coronary nitric oxide synthesis alter coronary vascular tone in normal dogs?
To examine whether endothelial nitric oxide formation contributes to the vascular tone of resistance coronary vessels in vivo, we administered NG-nitro-L-arginine methyl ester (L-NAME) (10 and 100 micrograms/kg/min), a nitric oxide synthase inhibitor, as well as D-enantiomer into the left circumflex artery in normal dogs. Intracoronary L-NAME, which was associated with dose-related reductions in acetylcholine-induced coronary vasodilation, significantly reduced the baseline left circumflex blood flow by 6% and increased coronary vascular resistance of the left circumflex artery by 6%. D-enantiomer was ineffective in altering baseline coronary blood flow and vascular resistance of the left circumflex artery. These results indicate that continuous nitric oxide formation in the vasculature is important in the regulation of the coronary vascular tone of resistance vessels in vivo, and serves to maintain the vessels in a dilated state.
Endo
T
T
First Department of Internal Medicine, Nippon Medical School, Tokyo, Japan.
Kaneko
H
H
Kiuchi
K
K
Fujita
S
S
Yamamoto
T
T
Takagi
G
G
Takahashi
N
N
Asai
K
K
Suzuki
I
I
Najima
J
J
Suzuki
Y
Y
Hayakawa
H
H
D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000378:metabolism*; D004285:Dogs; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D014655:Vascular Resistance / Q000187:drug effects
D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester