[Structural and metabolic characteristics of m. vastus lateralis of monkeys during 30-day hypokinesia: effects of prophylactic Gz-accelerations].

Studies of m. vastus lateralis in Rhesus monkeys exposed to weightlessness on board of the Russian biosatellites showed the profound changes of the muscle structural and metabolic profile. It is known that exposure to head-down tilt berets (BR) induces the similar changes though not so pronounced. It is supposed that the artificial gravity application is one of the promising countermeasure means purposed to prevent from the unfavourable effects of exposure to weightlessness. The present work was aimed to study the effects of the artificial gravity on structural and metabolic characteristics of hind-limb muscle in monkeys exposed to BR. 11 monkeys were subjected to 30 day 6 head down tilt BR.5 animals of them (group BR + Gz) were exposed also to daily rotation on the centrifuge (1.4 G for 5-20 min), the other animals (BR) were under only pure BR during the study. In BR animals the m. vastus lateralis slow-twitch (ST) and fast-twitch (FT) fiber size decreased by 25.4% and 12.7% respectively. In group BR + Gz the ST and FT fiber cross-sectional area was reduced by 18.7% and 8.1% respectively. The area percentage of the connective tissue compartment in BR animals increased from 4.6% to 6.8%. Capillary per fibre ratio was reduced by 9.6% and 8.6% in BR and BR + Gz monkeys respectively. The less pronounced level of capillary reduction as compared to level of fibre size decrease led to the increase of the capillary density by 13% in BR group, and no change in BR + Gz one. No changes in succinate dehydrogenase (SDH) activity were revealed in fibres of BR animals (this phenomenon may be the consequence of the proportional decrease of the oxidative potential and fibre size). In BR + Gz monkeys the SDH activity were found to be significantly elevated by 22.2% and 28.6% in ST and FT fibres respectively. Thus the data obtained show that chronic application of Gz tends to diminish the intensity of structural and metabolic changes in skeletal muscles under simulated microgravity.