title: Defective calcium handling in cardiomyocytes isolated from hearts subjected to ischemia-reperfusion.
abstract: Although ischemia-reperfusion (I/R) has been shown to affect subcellular organelles that regulate the intracellular Ca2+ concentration ([Ca2+]i), very little information regarding the Ca2+ handling ability of cardiomyocytes obtained from I/R hearts is available. To investigate changes in [Ca2+]i due to I/R, rat hearts in vitro were subjected to 10-30 min of ischemia followed by 5-30 min of reperfusion. Cardiomyocytes from these hearts were isolated and purified; [Ca2+]i was measured by employing fura-2 microfluorometry. Reperfusion for 30 min of the 20-min ischemic hearts showed attenuated cardiac performance, whereas basal [Ca2+]i as well as the KCl-induced increase in [Ca2+]i and isoproterenol (Iso)-induced increase in [Ca2+]i in cardiomyocytes remained unaltered. On the other hand, reperfusion of the 30-min ischemic hearts for different periods revealed marked changes in cardiac function, basal [Ca2+]i, and Iso-induced increase in [Ca2+]i without any alterations in the KCl-induced increase in [Ca2+]i or S(-)-BAY K 8644-induced increase in [Ca2+]i. The I/R-induced alterations in cardiac function, basal [Ca2+]i, and Iso-induced increase in [Ca2+]i in cardiomyocytes were attenuated by an antioxidant mixture containing superoxide dismutase and catalase as well as by ischemic preconditioning. The observed changes due to I/R were simulated in hearts perfused with H2O2 for 30 min. These results suggest that abnormalities in basal [Ca2+]i as well as mobilization of [Ca2+]i upon beta-adrenoceptor stimulation in cardiomyocytes are dependent on the duration of ischemic injury to the myocardium. Furthermore, Ca2+ handling defects in cardiomyocytes appear to be mediated through oxidative stress in I/R hearts.
authors.affiliation: Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, and Department of Physiology, University of Manitoba, Winnipeg, Canada.
authors.forename: Harjot K
authors.initials: HK
authors.lastname: Saini
authors.forename: Naranjan S
authors.initials: NS
authors.lastname: Dhalla
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002374:Catalase / Q000494:pharmacology; D002470:Cell Survival / Q000502:physiology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D066298:In Vitro Techniques; D019157:Ischemic Preconditioning, Myocardial; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000502:physiology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018342:Receptors, Adrenergic, beta-1 / Q000378:metabolism; D013482:Superoxide Dismutase / Q000494:pharmacology; D017725:Ventricular Pressure / Q000502:physiology
chemical_list: D000318:Adrenergic beta-Agonists; D002120:Calcium Channel Agonists; D016877:Oxidants; D018342:Receptors, Adrenergic, beta-1; D011189:Potassium Chloride; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase; D007545:Isoproterenol; D002118:Calcium