Mechanisms of Ca2+ overload induced by extracellular H2O2 in quiescent isolated rat cardiomyocytes.
Rat cardiomyocytes were exposed to H2O2 (1-100 micromol/L) for 10 min with washout for 10 min. Intracellular Ca2+ concentration ([Ca2+]i) was measured using fluo-3. [Ca2+]i increased with 100 micromol/L H2O2 and further increased during washout, causing irreversible contracture in one-half of the cells. The increase in [Ca2+]i with 10 micromol/L H2O2 was modest with few cells showing irreversible contracture and attenuated by caffeine, and [Ca2+]i gradually decreased during washout and this decrease was accelerated by a calcium-free solution, while 1 micromol/L H2O2 did not have any effects on [Ca2+]i or cell viability. Ca2+ overload caused during exposure to 100 micromol/L H2O2 was attenuated by caffeine with improved cellular viability but not by chelerythrine, KB-R7943 or nifedipine. With 100 micromol/L H2O2 calcium-free solution attenuated the increase during exposure and washout while KB-R7943 or chelerythrine partly attenuated further increase during washout but not improved cell viability, but chelerythrine did not have additional effect on calcium-free treatment. Catalase abolished the effects of H2O2. We concluded that the increased [Ca2+]i during exposure to 100 micromol/L H2O2 was caused both by release of Ca2+ from the intracellular store sites including the sarcoplasmic reticulum and by influx through route(s) other than the voltage-dependent Ca2+ channels or Na+/Ca2+ exchanger, although the Na+/Ca2+ exchanger or protein kinase C-mediated mechanism was partly responsible for a further increase during washout.
Gen
W
W
Department of Geriatrics, Keio University School of Medicine, Tokyo, Japan.
Tani
M
M
Takeshita
J
J
Ebihara
Y
Y
Tamaki
K
K
D000470:Alkaloids; D000818:Animals; D053119:Benzophenanthridines; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002374:Catalase / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D005609:Free Radicals / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D066298:In Vitro Techniques; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism*; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology; D015428:Myocardial Reperfusion Injury / Q000378:metabolism; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology*; D010617:Phenanthridines / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012508:Sarcolemma / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors
D000470:Alkaloids; D053119:Benzophenanthridines; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D005609:Free Radicals; D016877:Oxidants; D010617:Phenanthridines; D010726:Phosphodiesterase Inhibitors; D019831:Sodium-Calcium Exchanger; D002110:Caffeine; D006861:Hydrogen Peroxide; C016299:chelerythrine; D002374:Catalase; D009543:Nifedipine; D002118:Calcium