Effects of anoxia on intracellular Ca2+ and contraction in isolated guinea pig cardiac myocytes.
Single, enzymatically isolated guinea pig ventricular myocytes were exposed to 3-min periods of anoxia with glucose-free Tyrode solution containing 1 mM sodium dithionite (Na2S2O4) and were then reoxygenated for 10 min. The myocytes were exposed to rapid applications of 10 mM caffeine during the control, anoxic, and reoxygenation periods. Intracellular Ca2+ concentration ([Ca2+]i) was measured ratiometrically using indo 1 with simultaneous measurements of cell length. The effects of anoxia on Ca2+ were compared with those of hypoxia and metabolic inhibition. The amplitude of the electrically stimulated (Ca transient) and caffeine-evoked Ca2+ (Caff-Ca) transients decreased during anoxia and recovered after reoxygenation. Diastolic [Ca2+]i did not change during 3 min of anoxia but rose progressively after prolonged anoxia and remained at this higher level on reoxygenation. During metabolic inhibition the Ca transients decreased, while the Caff-Ca transients showed no change in amplitude. During hypoxia the Ca transients decreased. Anoxia slowed the time to peak of the Ca transient, the time to 50% relaxation, and the time to 90% relaxation. The decline of indo 1 fluorescence on rapid caffeine application was slowed during anoxia, metabolic inhibition, and hypoxia and partially recovered after reoxygenation.
Seki
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Department of Cardiac Medicine, National Heart and Lung Institute, University of London, United Kingdom.
MacLeod
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KT
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015687:Cell Hypoxia / Q000187:drug effects / Q000502:physiology; D003847:Deoxyglucose / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D017202:Myocardial Ischemia / Q000378:metabolism / Q000503:physiopathology; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000503:physiopathology; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*
D000963:Antimetabolites; D002110:Caffeine; D000255:Adenosine Triphosphate; D003847:Deoxyglucose; D002118:Calcium