[Peculiarities of development of muscular atrophy in rats of varying age due to suspension].
Compared were changes in m. soleus and m. gastrocnemius in rats at the age of 40, 100 and 220 days in a 30-d experiment with tail suspendion. As it was stated, deficient support loading of the hind limbs had a negative effect on the gain in m. soleus mass and, to a less degree, in m. gastrocnemius mass, particularly in younger rats. In tail-suspended young rats m. soleus mass was by 60% and in elder rats by 48% less as compared to their controls. No matter age of the group, type-1 fibers and IIA and IIC in m. soleus were equally affected. In comparison with the controls, cross-section areas of fibers in 40- and 100-d old rats decreased by 62-68% and in 220-d old rats, by 43-50%. Slow type 1 muscular fibers underwent transformation in fast type IIA and IIC fibers in m. soleus. The more aged rats, the less population of slow muscular fibers transformed. The m. gastrocnemius mass in all suspended groups was by 20% lower than in the controls. In 40- and 100-d old rats suspension caused atrophy of each of 5 types of fibers in m. gastrocnemius, whereas in 220-d old rats those were only types IA and IIC of fibers that had been atrophied. There were early signs of transformation of slow type IB fibers in the fast ones. The conclusion was made that muscles of young animals are more sensitive to deficit in functional loading and atrophy more severely that in old rats. Transformation of slow fibers was observed mainly in m. soleus of young animals and was essentially absent in old.
Il'ina-Kakueva
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EI
D000367:Age Factors; D000818:Animals; D001284:Atrophy / Q000209:etiology / Q000473:pathology; D001835:Body Weight; D018476:Hypokinesia / Q000150:complications; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology*; D011187:Posture; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors