[Histochemical and biochemical changes in skeletal muscles of rhabdomyolysis-sensitive racehorses following exertion. III: Elevated activity of various antioxidant enzymes].

In this communication, the results of a histochemical and biochemical enzyme study on gluteus medius muscle of horses, sensitive to exertional myopathy, during attacks of rhabdomyolysis are presented. For the biochemical study the biopsy specimens investigated were selected by means of histological and enzyme histochemical staining methods. Dissected specimens were used which contained groups of muscle fibres with a high or low activity of glucose-6-phosphate dehydrogenase. The activity of glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase, glutathione reductase, glutathione peroxidase, superoxide dismutase, and catalase was measured microbiochemically in these dissected specimens. A rise in activity of glucose-6-phosphate dehydrogenase in pathologically changed muscle fibres was always found to be coupled with a significant rise in activity of phosphogluconate dehydrogenase, glutathione reductase, and glutathione peroxidase. In these muscle fibres, the activity of superoxide dismutase and catalase was not significantly increased. On the basis of the combined histochemical and biochemical findings it is concluded that the application of the histochemical method for the demonstration of glucose-6-phosphate dehydrogenase activity can be highly recommended for the study of antioxidant enzymes in skeletal muscles with neuromuscular defects.