Prior heat stress improves survival of ischemic-reperfused skeletal musclein vivo

The ability of heat stress to improve the survival of ischemic-reperfused s keletal muscle in vivo was investigated. Ischemia-reperfusion was applied u sing the rat hindlimb tourniquet model. The viability of ischemic-reperfuse d muscle (11 +/- 1%) was increased by prior mild heat stress (86 +/- 2%). T o investigate whether heat shock protein 70 (Hsp 70) expression in the musc le of the heated limb was responsible for this protection, the survival of Hsp 70-expressing transduced myoblasts and myocytes was measured after expo sure to mediators of ischemia-reperfusion injury. Survival was improved in Hsp 70-positive myoblasts but not in myocytes, suggesting that the mechanis m of protection conferred by heat stress in vivo cannot be explained by the expression of Hsp 70 in myocytes and may involve a more complex mechanism. In conclusion, prior heat stress is effective in protecting mature skeleta l muscle in vivo against necrosis after ischemia-reperfusion and has potent ial for use in microsurgical procedures requiring tourniquet applications. (C) 2000 John Wiley & Sons, Inc.