Function of fast- and slow-twitch rat skeletal muscle following ischemia and reperfusion at different intramuscular temperatures

Fast- (peroneal) and slow-twitch (soleus) skeletal muscles of anesthetized Wistar rats were subjected to 3 h of tourniquet ischemia. The intramuscular temperature of the leg was adjusted to 22, 30 or 35 degrees C (n = 12 per group) during ischemia. After 2 h of reperfusion, the muscles were electric ally stimulated in vitro and muscular function was analyzed for maximal for ce, performance, contractility and fatigue. Contralateral nonischemic muscl es served as controls. Three hours of ischemia at 30 degrees C did not redu ce the function of the peroneal muscles compared to nonischemic controls. T he same ischemic stress significantly reduced the function of the soleus mu scles compared to nonischemic controls. The postischemic function of the so leus muscles declined with increasing temperature. The postischemic functio n of the 35 degrees C group of peroneal muscles was significantly reduced c ompared to the 22 and the 30 degrees C groups, which did not differ. These results provide evidence that fast-twitch muscles are more resistant to isc hemia than slow-twitch muscles. They furthermore show a fiber type-specific dependency of postischemic muscle function on intramuscular temperature du ring ischemia. Hypothermia-sensitive fast-twitch fibers predominate in the skeletal muscles of the extremities. Mild hypothermia could, therefore, red uce tourniquet ischemia-induced injury after surgery of the extremities. Co pyright (C) 2000 S. Karger AG. Basel.