Hypoxia-dependent changes of enzyme activities in different fibre types of rat soleus and extensor digitorum longus muscles. A cytophotometrical study.

Using cytophotometry activity changes of succinate dehydrogenase, glycerol-3-phosphate dehydrogenase and myofibrillar adenosine triphosphatase were measured in 3 fibre types of soleus and extensor digitorum longus muscles under normal and experimental conditions. Fibres were typed by means of cytophotometrical data into slow-oxidative, fast-oxidative glycolytic and fast-glycolytic ones. After experimental hypoxia of 20 min duration a significant increase of enzyme activities was observed especially in slow-oxidative and fast-oxidative glycolytic fibres of both muscles, e.g. succinate dehydrogenase activity increased by 21% in these fibres of soleus muscle and by 23-26% in these fibres of extensor digitorum longus muscle. Moreover, an increase of glycerol-3-phosphate dehydrogenase activity by 10% in slow-oxidative fibres and by 28% in fast-oxidative glycolytic fibres and a 10-12% increased ATPase activity in all fibres of extensor digitorum longus muscle were measured. Treatment with Ginkgo biloba extract for 3 months before exposure to hypoxia resulted in increased adenosine triphosphatase activity in all fibres of both muscles and in decreased succinate dehydrogenase activity of slow-oxidative and fast-oxidative glycolytic fibres of extensor digitorum longus muscle. These results could be interpreted as a protective effect of Ginkgo biloba extract.