THE FUNCTIONAL AND MORPHOLOGICAL DAMAGE OF ISCHEMIC-REPERFUSED SKELETAL-MUSCLE

Skeletal muscle is frequently damaged by ischemia-reperfusion both cau sed by direct injury and also by surgery. The purpose of the present e xperiments was to examine how the different types of skeletal muscles (fast and slow) react functionally and morphologically after 1 and 2 h of ischemia followed by different periods of reperfusion. The fast-tw itch (musculus extensor digitorum longus, EDL) and the slow-twitch (mu sculus soleus, SOL) muscle of Wistar rats were prepared. They were sti mulated in vivo, either directly or indirectly at different reperfusio n times following tourniquet ischemia, and the contraction force of th e muscles was recorded. The morphological changes were examined by lig ht microscopy. At early reperfusion times, the contraction force of th e EDL muscle was reduced by 40 and 90% after 1 and 2 h of ischemia, re spectively. The contraction farce was about 50% at the end of a 2-week reperfusion period in the 1-hour ischemia group and it increased sign ificantly (from 5 to 38%) during the second week if the ischemia laste d for 2 h. Reduction of contraction force in the SOL muscle was over 5 0 and 90% following 1 and 2 h of ischemia, respectively, and it starte d to improve from the 2nd week. Morphological changes of the two types of muscle were identical. At early reperfusion times granulocytes wer e seen in the blood vessels adhering to the endothelium. 24 h later ne utrophil granulocytes migrated into the endomysium and thereafter into the perimysium. One week after 1 h of ischemia both muscles showed no rmal histology. However, the structural regeneration process only star ted at the end of the 1st week of reperfusion after 2 h of the ischemi c damage. The following conclusions can be drawn. (1) There is functio nal morphological evidence of ischemic and reperfusion injury in both muscles after 24 h and also after 1 week of reperfusion. (2) Functiona lly, the two types of muscles regenerate differently, i.e. the SOL sta rts to regenerate earlier than the EDL. (3) Morphologically the two ty pes of muscle show the same reactions. An increase in the time of isch emia from 1 to 2 h delays the regeneration processes.