Differential contribution of nitric oxide to regulation of vascular tone in coronary conductance and resistance arteries: intravascular ultrasound studies.
We examined the role of nitric oxide in the maintenance of coronary vascular tone in 15 dogs. A 0.014 inch Doppler wire was introduced into the midsegment of the circumflex coronary artery and a 4.3F, 30 MHz two-dimensional ultrasound imaging catheter was introduced over the Doppler wire. Acetylcholine caused a dose-dependent vasodilation in both epicardial and resistance coronary arteries. However, N omega-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthetase caused a dose-dependent vasoconstriction mainly in the epicardial coronary arteries, partially reversed by L-arginine. The vasodilator response to acetylcholine was inhibited by L-NAME only in the epicardial circulation. Thus using combined intracoronary two-dimensional and Doppler ultrasound, we have demonstrated both basal and acetylcholine-induced release of nitric oxide in epicardial coronary arteries. The failure of L-NAME to decrease basal and acetylcholine-induced increases in flow velocity suggests that endothelium-dependent relaxation in coronary resistance vessels may not be mediated by nitric oxide alone.
Sudhir
K
K
Cardiovascular Research Institute, University of California at San Francisco 94143.
MacGregor
J S
JS
Amidon
T M
TM
Gupta
M
M
Yock
P G
PG
Chatterjee
K
K
D000109:Acetylcholine / Q000502:physiology*; D000594:Amino Acid Oxidoreductases / Q000187:drug effects; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001783:Blood Flow Velocity / Q000187:drug effects; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000187:drug effects / Q000502:physiology*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D019001:Nitric Oxide Synthase; D018084:Ultrasonography, Interventional; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester