ONTOGENIC TRANSFORMATIONS OF ENERGY-METAB OLISM IN SKELETAL-MUSCLE UNDER DIFFERENT CONDITIONS OF ANIMAL DEVELOPMENT

Age-related changes in the general activity of creatin kinase (CrK), m itochondrial fraction of this enzyme (CrKmit), general activity of lac tate dehydrogenase (LDH) and its anaerobic fraction (LDHan), content a nd ratio of cytochromes of the mitochondrial respiration chain, respir ation rate of isolated mitochondria on various substrates in the 3rd s tate have been studied in the skeletalmuscle of Wistarrats developing under the conditions of normo- (NK) and hypokinesia (HK). General patt erns of changes in these indices have been shown, that do not depend o n the conditions of animal development: the minimal CrK and CrKmit act ivity and increased saturation of the respiration chain with cytochrom e b562 during the playing period, days 30 to 40 of postnatal period. T he highest level of cytochrome aa3 Was observed in the peak of sexual maturation (Day 45). However the conditions of development affect the timing of extremal indices and their level in adult animals. For examp le, in the animals developing under the NK conditions the highest satu ration of the respiration chain with cytochrome b562 was observed on D ay 30, while in those developing under the HK conditions by five days later. In 30-day old rats from the NK group the cytochrome aa3 content of skeletal muscle was almost maximal, while in the HK group the maxi mum was observed only at the peak of sexual maturation. In the adult a nimals of the HK group the activity of CrKmit, LDH and LDHan was highe r, while the content of cytochrome aa3 and saturation of the respirati on chain with cytochrome b562 was lower. A lesser b562/aa3 ratio is re lated to the predominance of NADH2-dependent electron transport pathwa ys of oxidation in the mitochondria from the rat skeletal muscle. Thus , the conditions of development in the early postnatal period, especia lly during the playing period, determine the state of energy metabolis m in the adult skeletal muscle.