Contribution of nitric oxide to dilation of resistance coronary vessels in conscious dogs.
Endothelium-dependent relaxation of conductance coronary vessels involves nitric oxide formation from L-arginine. The present study examines whether a similar mechanism intervenes in the vasomotor control of resistance coronary vessels. In conscious dogs, the excess of coronary blood flow (CBF) created by intracoronary acetylcholine (3.0 ng/kg) averaged 7.2 +/- 1.1 ml. Intracoronary adenosine (100 ng/kg) increased CBF by 12.4 +/- 1.4 ml. Intracoronary nitroglycerin (175 ng/kg) increased CBF by 7.4 +/- 1.2 ml. CBF repayment-to-debt ratio after a 15-s coronary arterial occlusion averaged 2.8 +/- 0.2. After an intracoronary N omega-nitro-L-arginine dose (10 micrograms.kg-1.min-1 x 12 min) was given to inhibit nitric oxide formation, baseline CBF was not altered. CBF increases with acetylcholine averaged 2.4 +/- 0.5 and 6.4 +/- 0.7 ml with adenosine, both less (P less than 0.01) than responses before the arginine analogue. CBF increases with nitroglycerin averaged 7.2 +/- 1.1 ml, similar to control responses. CBF repayment-to-debt ratio during reactive hyperemic responses fell (P less than 0.01) to 1.7 +/- 0.1. L-Arginine (1.0 mg.kg-1.min-1 x 12 min) partially reversed the inhibitory effect of the arginine analogue on CBF responses to acetylcholine. Thus nitric oxide formed in resistance coronary vessels is a major mediator of coronary vasodilation to acetylcholine, adenosine and transient ischemia.
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Department of Physiology, University of Montreal, Quebec, Canada.
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D000109:Acetylcholine / Q000494:pharmacology; D000241:Adenosine / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001810:Blood Volume / Q000187:drug effects; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000187:drug effects*; D004285:Dogs; D009569:Nitric Oxide / Q000494:pharmacology*; D019335:Nitroarginine; D005996:Nitroglycerin / Q000494:pharmacology; D014655:Vascular Resistance; D014664:Vasodilation / Q000187:drug effects*
D019335:Nitroarginine; D009569:Nitric Oxide; D001120:Arginine; D005996:Nitroglycerin; D000241:Adenosine; D000109:Acetylcholine