SERIAL MORPHOMETRIC CHANGES IN SKELETAL-MUSCLE FIBERS DURING REPERFUSION

A histochemical, morphometric method was employed for sequential inves tigation of the changes occurring in primate skeletal muscle during th e first 24 hours of reperfusion following 3 hours of tourniquet-induce d ischaemia. While there was a general reduction in mean fibre diamete rs after ischaemia, fibre types 1, 2A and 2B were found to respond dif ferently to reperfusion over the experimental period, Type 1 fibres we re significantly enlarged after 6, 12, 18 and 24 hours of reperfusion, with type 2A fibres being significantly enlarged after 12, 18 and 24 hours. The trend of enlargement for type 2B fibres did not reach stati stical significance. The degree of oedema, expressed as a percentage i ncrease in fibre diameter, varied in the different fibre types, being greatest in type 1 fibres and least in type 2B. These differences in r esponse may reflect the fibre type's metabolic dependence on oxygen. T his study provides a baseline of morphometric changes in the three mai n fibre types following a fixed period of ischaemia and reperfusion, T he model may prove useful in the evaluation of pharmacological protect ion of ischaemic skeletal muscle.