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Journal of The Korean Society of Emergency Medicine 1999;10(2): 208-219. |
| Effect of Ischemic Preconditioning on the Functional Recovery of Myocardium: Isolated heart experimental study |
| Young Jin Cheon, Jun Sig Kim, Seung Baik Han, Kwang Je Baek, In Sung Lee |
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| ABSTRACT |
BACKGROUND: Brief episode of coronary artery occlusion (i.e., ischemic preconditioning) makes the heart more resistant to injury from a subsequent ischemic insult.
Although a great deal of effort has been made in studying ischemic preconditioning, the underlying mechanism of ischemic preconditioning and its effect on hypothermic insult has not been elucidated. This study was performed to see whether ischemic preconditioning protects against the depression of cardiac contractility induced by hypothermic cardioplegic arrest/reperfusion. And recently, adenosine was known to have some correlation with the mechanism of preconditioning. If so, does this effect remain after the blockade of adenosine receptor by 8-phenyl theophylline? METHOD: Twenty-four Sprague-Dawley rat weighed 250-350g were used and divided into three groups. Rat hearts were removed rapidly, and each isolated heart paced with a rate of 180/min was perused by modified Krebs-Hensleit buffer(KHB) solution on a Langendorff apparatus far an hour. After obtaining baseline data including left ventricular pressure(LVP), dp/dt, and coronary flow, cardiac arrest was induced by perfusion of 0degrees C crystalloid cardioplegic(St Thomas) solution. After that, all hearts were stored in the same St Thomas solution at salute temperature far 2 hours. In group I (control group), the hear was reperfused by KHB solution. In group II(preconditioning group), the heart was subjected to two 2-minute episode of global ischemia followed by 5 minute reperfusion with KHB solution(preconditioning) before cardiac arrest. In group III(phenyl theophylline group), the heart was subjected to preconditioning procedure and 8-phenyl theophylline at 10muM in concentration was added to KHB solution at time of reperfusion. Observing parameter was obtained in each group at 10, 20, 40 and 60 minutes after starting reperfusion and compared statistically by use of one way ANOVA test(STASTICA, release 4.5). P-value less than 0.05 was considered significant.
RESULTS:
Although depressed LVP, dp/dt, and Coronary flow were seen in all groups during the reperfusion period, the preconditioned group showed more effective recovery of LVP than that of the control group, especially at 10, 20 and 40 minutes(p<.05). We failed to demonstrate the difference between the phenyl theophylline group and the control group(p=NS).
CONCLUSION:
These results suggest that ischemic preconditioning has protective effect on recovery state of hypothermic cardioplegic arrest/reperfusion. Its protective effect was limited during early reperfusion stage and was blocked by adenosine blocker. |
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