Histochemical studies of striated muscle after temporary ischemia in the rat.

Temporary ischaemia of the hind linb of the rat was produced using a tourniquet with controlled pressure. Changes in the muscle seen after Gomori trichrome staining and after histochemical reactions for NADHdiaphorase, ATPases and phosphorylase were correlated with the duration of the ischaemia and the time of recovery. Histopathological changes were seen first after 2 h of ischaemia and increased thereafter; necrosis of most of the muscles occurred between 4 and 6 h of ischaemia. Necrosis and phagocytosis of muscle fibres and later the amount of regenerating fibres with characteristic histochemical staining properties increased linearly with increasing duration of ischaemia. Even after the most severe lesions of seemingly total necrosis of the muscle after 6 h of ischaemia most of the muscle regenerated within 18 days. Morphological alterations such as variation in fibre size, split fibres and central nuclei were still observed 226 days after ischaemia at which time the follow-up was terminated. Fibre type grouping was seen first after 45-90 days subsequent to 4 and 6 h ischaemia after incubation for ATPase, indicating concomitant neurogenic lesion in addition to the direct ischaemia of the muscle fibres.