[Skeletal musculature of rats during modeling of the physiological effects of weightlessness (morphological study)].

In the experiment rats were suspended in the head-down position (at -15 to -20 degrees) for 21 days. To study the effect of this exposure on skeletal muscles of their fore- and hindlimbs, morphological and histochemical methods were used. Changes in the hindlimbs were similar to those seen in real weightlessness of similar duration. The two antigravitational muscles - soleus and gastrocnemius muscles - showed greatest changes, i.e. atrophic and metabolic shifts. The biceps brachii muscle that changes insignificantly in the weightless state developed a destructive process (with degradation of myofibers) that was later replaced with a reparative process. The changes in this muscle are assumed to be associated with hemodynamic disorders. It is recognized that the method of rat suspension is adequate for a ground-based study of morphological effects of weightlessness on hindlimbs and is unacceptable for that of forelimbs where the exposure induces microcirculation disorders.