Space flight effect upon the bioenergetics of the skeletal muscles in rats.

Studies of tissue bioenergetics are very important to gain insight into the effects of weightlessness on the animal and human body. A reduction of the muscular load in zero gravity should affect reactions of biological oxidation because their pattern and level are related to energy requirements of the body. After the 22-day flight of the Cosmos 605 biosatellite tissue respiration and oxidative phosphorylation (P/O coefficient) in skeletal muscles of rats was investigated. The investigations showed that on the 2nd post-flight day oxidation assimilation by the muscle tissue was reduced compared with the control. In addition, the intensity of phosphorylation which determines the rate of ATP formation was decreased. These changes may reduce significantly the energy potential of the muscle cell and seem to form the basis for the functional inadequacy of skeletal muscles which can be found in men during the first post-flight days. At later stages (the 26th post-flight day) oxygen consumption and phosphorylation rate increased and reached the control level. Therefore, readaptation to the earth gravity is followed by adaptive changes in the processes responsible for the accumulation and utilization of the energy of biological oxidation.