The Mechanism of Tolerance against Hypothermia and Ischemia in Hibernators

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Objective : We have investigated the mechanism of tolerance against hypothermia and ischemia in deep hibernators in attempt to apply a hibernation phenomenon in cardiovascular surgery.Methods : Isolated hearts from hibernating and non-hibernating squirrels were rendered ischemia for 30 minutes at 37℃ or preserved in UW solution for 2 hours. Left ventricular function was evaluated by inflating the left ventricular balloon at a volume between 20-200 μL. Myocardial infarction was assessed by triphenyl-tetrazollum chloride staining. The number of apoptotic myocytes was calculated by a TUNEL method.Results : Left ventricular function, infarct size and the number of apoptotic myocytes were not significantly different between the hearts from hibernating and non-hibernating squirrels. In contrast, these parameters were significantly improved in the hearts from hibernating squirrels compared to non-hibernating squirrels.Conclusions : These results suggest that the hearts from hibernating squirrels are not signiflcantly tolerated to normothermic ischemia, but is resistant to myocyte deth during hypothermic preservation. Therefore, it is suggested that application of a hibernation phenomenon will be a promising approach in long term cardiac preservation.