title: Rapid adaptation of myocardial calcium homeostasis to short episodes of ischemia in isolated rat hearts.
abstract: Short episodes of ischemia and reperfusion (ischemic preconditioning) have been shown to attenuate the detrimental rise in intracellular free Ca2+ ([Ca2+]i) caused by subsequent sustained ischemia. The purpose of this study was to investigate the detailed time course of [Ca2+]i during such short episodes of ischemia and reperfusion. [Ca2+]i was measured at a high time resolution by surface fluorometry and indo-1 in isolated perfused rat hearts during three episodes of 5 minutes of ischemia followed by 5 minutes of reperfusion. We found that the rise in systolic [Ca2+]i was significantly smaller during the second (191% +/- 67%) and third (194% +/- 75%) episodes of ischemia than during the first episode (289% +/- 75%, P < 0.05 vs both subsequent episodes). This attenuated rise in systolic [Ca2+]i was preserved during perfusion with low extracellular Na+ (105.5 mmol/L [Na+]o). During short episodes of ischemia and reperfusion, [Ca2+]i rises less during the second and third ischemic episode than during the first episode. Thus one transient ischemic stimulus led to a rapid adaptation of [Ca2+]i homeostasis to subsequent ischemic conditions. Such a rapid adaptation might be an important mechanism of the ischemic preconditioning phenomenon in protecting against ischemic injury.
authors.affiliation: Department of Medicine and Cardiovascular Research Institute, University of California, San Francisco, USA.
authors.forename: G B
authors.initials: GB
authors.lastname: Smith
authors.forename: T
authors.initials: T
authors.lastname: Stefenelli
authors.forename: S T
authors.initials: ST
authors.lastname: Wu
authors.forename: J
authors.initials: J
authors.lastname: Wikman-Coffelt
authors.forename: W W
authors.initials: WW
authors.lastname: Parmley
authors.forename: C E
authors.initials: CE
authors.lastname: Zaugg
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006706:Homeostasis; D017202:Myocardial Ischemia / Q000378:metabolism* / Q000503:physiopathology; D015425:Myocardial Reperfusion; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D012964:Sodium / Q000378:metabolism; D013599:Systole; D013997:Time Factors; D017725:Ventricular Pressure
chemical_list: D012964:Sodium; D002118:Calcium