title: Attenuation of extracellular ATP response in cardiomyocytes isolated from hearts subjected to ischemia-reperfusion.
abstract: Extracellular ATP is known to augment cardiac contractility by increasing intracellular Ca2+ concentration ([Ca2+]i) in cardiomyocytes; however, the status of ATP-mediated Ca2+ mobilization in hearts undergoing ischemia-reperfusion (I/R) has not been examined previously. In this study, therefore, isolated rat hearts were subjected to 10-30 min of global ischemia and 30 min of reperfusion, and the effect of extracellular ATP on [Ca2+]i was measured in purified cardiomyocytes by fura-2 microfluorometry. Reperfusion for 30 min of 20-min ischemic hearts, unlike 10-min ischemic hearts, revealed a partial depression in cardiac function and ATP-induced increase in [Ca2+]i; no changes in basal [Ca2+]i were evident in 10- or 20-min I/R preparations. On the other hand, reperfusion of 30-min ischemic hearts for 5, 15, or 30 min showed a marked depression in both cardiac function and ATP-induced increase in [Ca2+]i and a dramatic increase in basal [Ca2+]i. The positive inotropic effect of extracellular ATP was attenuated, and the maximal binding characteristics of 35S-labeled adenosine 5'-[gamma-thio]triphosphate with crude membranes from hearts undergoing I/R was decreased. ATP-induced increase in [Ca2+]i in cardiomyocytes was depressed by verapamil and Cibacron Blue in both control and I/R hearts; however, this response in I/R hearts, unlike control hearts, was not affected by ryanodine. I/R-induced alterations in cardiac function and ATP-induced increase in [Ca2+]i were attenuated by treatment with an antioxidant mixture and by ischemic preconditioning. The observed changes due to I/R were simulated in hearts perfused with H2O2. The results suggest an impairment of extracellular ATP-induced Ca2+ mobilization in I/R hearts, and this defect appears to be mediated through oxidative stress.
authors.affiliation: Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, 351 Tache Ave., Winnipeg, MB, Canada R2H 2A6.
authors.forename: Harjot K
authors.initials: HK
authors.lastname: Saini
authors.forename: Vijayan
authors.initials: V
authors.lastname: Elimban
authors.forename: Naranjan S
authors.initials: NS
authors.lastname: Dhalla
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002374:Catalase / Q000494:pharmacology; D015687:Cell Hypoxia; D002469:Cell Separation; D045604:Extracellular Fluid / Q000378:metabolism*; D016166:Free Radical Scavengers / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism; D019157:Ischemic Preconditioning, Myocardial; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000378:metabolism* / Q000473:pathology; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D009994:Osmolar Concentration; D016877:Oxidants / Q000494:pharmacology; D010100:Oxygen / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013482:Superoxide Dismutase / Q000494:pharmacology
chemical_list: D000318:Adrenergic beta-Agonists; D016166:Free Radical Scavengers; D016877:Oxidants; D000255:Adenosine Triphosphate; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase; D007545:Isoproterenol; D010100:Oxygen; D002118:Calcium