Coronary artery contractility, Na(+)-pump and oxygen radicals.
Oxygen radicals accumulated during ischemia and reperfusion may affect coronary contractility by endothelium dependent and independent pathways one of which may involve Na(+)-pump. Here we report a contractility assay for Na(+)-pump in pig coronary artery and use it to examine the effects of hydrogen peroxide and superoxide. Coronary artery rings contracted in a K(+)-free Krebs solution and relaxed upon subsequent exposure to K+. The relaxation approximated a single exponential decay whose rate constant depended on [K+]2. This K(+)-induced relaxation was abolished by ouabain and was attributed to Na(+)-pump. In tissues pretreated with peroxide, the rate of relaxation of the K(+)-free contracted arteries decreased with an IC50 = 1.6 +/- 0.6 mmol/l for peroxide. Another set of tissues was pretreated with the superoxide generating system containing 0.3 mmol/l xanthine + varying concentrations of xanthine oxidase (XO) and precontracted in K(+)-free Krebs solution. The rate of the K(+)-induced relaxation decreased with IC50 = 24 +/- 8 mU/ml for XO. Thus, using the relaxation assay we conclude that exposing coronary arteries to oxygen radicals can damage Na(+)-pumps.
Elmoselhi
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Department of Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
Butcher
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Samson
S E
SE
Grover
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AK
D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D017202:Myocardial Ischemia; D015425:Myocardial Reperfusion; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013481:Superoxides / Q000494:pharmacology*; D013552:Swine; D013997:Time Factors; D019820:Xanthine; D014969:Xanthine Oxidase / Q000378:metabolism; D014970:Xanthines / Q000378:metabolism
D014970:Xanthines; D013481:Superoxides; D019820:Xanthine; D010042:Ouabain; D006861:Hydrogen Peroxide; D014969:Xanthine Oxidase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium