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Infarct limitation of the second window of protection in a conscious rabbit model

Yang, XM; Baxter, GF; Heads, RJ; Yellon, DM; Downey, JM; Cohen, MV; (1996) Infarct limitation of the second window of protection in a conscious rabbit model. CARDIOVASC RES , 31 (5) 777 - 783.

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Abstract

Objectives: Myocardial protection associated with ischemic preconditioning (PC) wanes within an hour or two. It has recently been observed, however, that a delayed phase of protection appears about 24 h after ischemic PC in anesthetized rabbits and dogs which might be related to synthesis of cytoprotective proteins. We tested whether a second window of protection could be induced in conscious rabbits. Methods: Rabbits chronically instrumented with a coronary artery occluder and ECG electrodes experienced a 30-min coronary occlusion followed by 3 h reperfusion. Infarct size was measured with triphenyltetrazolium chloride. Results: 35.7 +/- 2.3% of the risk zone infarcted in control animals. PC with 4 cycles of 5-min coronary occlusion/10-min reperfusion 24 h prior to the 30-min ischemia decreased infarction to 24.1 +/- 1.4% of the risk zone (P < 0.01). During the 30-min occlusion 3 of 7 non-PC rabbits developed ventricular fibrillation, while this arrhythmia did not occur in the 7 PC animals (P < 0.1). Myocardial hsp70 content in PC rabbits was twice that in controls. Collateral blood flow was not different in the two groups. Conclusions: A second window of protection exists in conscious rabbits which minimizes both infarction and arrhythmias, and cytoprotective protein content is increased in the myocardium of protected animals.

Type:Article
Title:Infarct limitation of the second window of protection in a conscious rabbit model
Keywords:collateral vessels, heat shock protein, myocardial infarction, myocardial ischemia, preconditioning, arrhythmias, myocardial protection, myocardial infarct size, rabbit, ISCHEMIA, PROTEIN, STRESS
UCL classification:UCL > School of Life and Medical Sciences > Faculty of Population Health Sciences > Institute of Cardiovascular Science

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