The functional damages of ischemic/reperfused skeletal muscle

Skeletal muscle is frequently damaged by ischemia-reperfusion when exposed to direct injury or in the surgical practice. The purpose of the present experiments was to examine how the different types of skeletal muscles (fast & slow) react functionally to one and two hours of ischemia followed by two weeks of reperfusion. The fast-twitch (m. extensor digitorum longus/EDL) and the slow-twitch (m. soleus/SOL) muscle were prepared. They were stimulated, in vivo, either directly or indirectly at different reperfusion times following tourniquet ischemia, and the contraction force (CF) was recorded. CF of the EDL was reduced over 40% and 90% of the control value during the first 24 hours of reperfusion after 1 and 2 hours of ischemia, respectively. It was about 50% at the end of the 2nd week in the one-hour group. CF increased significantly during the second week if ischemia lasted for two hours. Reduction of CF in the SOL muscle was over 50% and 90% following one and two hours of ischemia, respectively. It further decreased in the 1-hour group, and it started to regenerate from the second week after 2 hours of ischemia. It is concluded that 1. two hours of ischemia causes significantly more severe damages in both types of skeletal muscles than one hour. 2. There is a reperfusion injury in both muscles during the first week of reperfusion. 3. The two types of muscles regenerate differently, i.e. the SOL starts to regenerate earlier than the EDL.