Endothelium-mediated regulation of coronary tone.
To what extent endothelial autacoids like endothelium-derived relaxant factor/nitric oxide (EDRF/NO), in addition to neural-humoral factors, are involved in the regulation of myocardial perfusion, is presently not known. Therefore, we investigated in conscious, chronically instrumented dogs the effect of stereospecific inhibitors (NG-monomethyl-L-arginine (L-NMMA), NG-nitro-L-arginine (L-NNA), NG-monomethylester-L-arginine (L-NAME] of nitric oxide-synthesis and -release on epicardial coronary tone (and coronary diameter) and myocardial perfusion. A hydraulic coronary cuff was used, to produce reactive hyperemia and to keep the myocardial perfusion constant over short periods. 40 mg/kg L-NNA i.v. caused a long-lasting increase in mean arterial blood pressure from 94 +/- 8 to 129 +/- 11 mmHg and a simultaneous decrease in coronary diameter by 2.8 +/- 0.3%. Heart rate dropped from 87 to 58 min-1, but the double product of heart rate and blood pressure dropped by only 8 +/- 2% (p = 0.05). The maximal coronary conductance during peak reactive hyperemia (after 20 s ischemia) indicating complete coronary dilation was diminished by 48% after L-NNA. The severe drop in resting myocardial perfusion and O2-supply, and nearly unchanged rate pressure product and thus myocardial metabolic rate following the inhibition of nitric oxide formation demonstrate a substantial contribution of EDRF/NO to the regulation of myocardial perfusion.
Bassenge
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Lehrstuhl für Angewandte Physiologie der Universität Freiburg, FRG.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology; D004285:Dogs; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D006321:Heart / Q000502:physiology*; D006439:Hemodynamics / Q000187:drug effects; D009129:Muscle Tonus / Q000187:drug effects / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000378:metabolism; D019323:omega-N-Methylarginine
D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester