Differential actions of L-cysteine on responses to nitric oxide, nitroxyl anions and EDRF in the rat aorta.
1. The effects of L-cysteine were tested in rat aortic rings on responses to nitric oxide free radical (NO(*)), nitroxyl (NO(-)) derived from Angeli's salt and endothelium-derived relaxing factor (EDRF) activated by acetylcholine, ATP and the calcium ionophore A23187. Concentrations of 300 microM or less of L-cysteine had no effect on responses. 2. Relaxations produced by exogenous NO(*) (0.25 - 2.5 microM) were markedly prolonged and relaxations produced by sodium nitroprusside (0.001 - 0.3 microM) were enhanced by 1 and 3 mM L-cysteine. The enhancements by L-cysteine of responses to NO(*) and sodium nitroprusside may be attributed to the formation of S-nitrosocysteine. 3. Relaxations mediated by the nitroxyl anion (0.3 microM) donated from Angeli's salt were more prolonged than those produced by NO(*), and nitroxyl-induced relaxations were reduced by L-cysteine (1 and 3 mM). 4. EDRF-mediated relaxations produced by acetylcholine (0.01 - 10 microM), ATP (3 - 100 microM) and the calcium ionophore A23187 (0.1 microM) were significantly reduced by 3 mM L-cysteine. 5. The similarity between the inhibitory effects of L-cystei on responses to EDRF and on those to nitroxyl suggests that a component of the response to EDRF may be mediated by nitroxyl anion.
Ellis
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Pharmacology Research Unit, Department of Medical Laboratory Science, RMIT University, GPO Box 2476V, Melbourne, Victoria, 3001, Australia.
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D000109:Acetylcholine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects*; D000001:Calcimycin / Q000494:pharmacology; D003545:Cysteine / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology; D005609:Free Radicals; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009569:Nitric Oxide / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009589:Nitrogen Oxides / Q000494:pharmacology*; D009599:Nitroprusside / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D005609:Free Radicals; D020030:Nitric Oxide Donors; D009589:Nitrogen Oxides; D014662:Vasoconstrictor Agents; D009599:Nitroprusside; D010656:Phenylephrine; D009569:Nitric Oxide; D000001:Calcimycin; D000255:Adenosine Triphosphate; C039900:nitroxyl; D003545:Cysteine; D000109:Acetylcholine