[Content of energy substrates in fibers of postural muscle soleus and its antagonist in the condition of support deprivation].

The investigation had the purpose to measure energy substrates in different fibers of 3- and 14-d suspended postural m. soleus and its main antagonist - anterior tibial muscle in rats. Hindlimb suspension served as a model of gravitational unloading. After suspension, left m. soleus or anterior tibial muscle was extracted. Serial cross-sections were subject to histochemical staining by Oil Red O (Sigma) for determination of intracellular triglycerides or by Schiff's reagent and iododic acid (Sigma-ALDRICH) for determination of glycogen and simultaneous immunohistochemical fibers typing by antibodies to heavy types I and II myosin chains (NCL-MHCs and NCL-MHCf, Novocastra). Analysis of intracellular energy substrates showed that both types of fibers in the anterior tibial muscle had accumulated triglycerides by week-2 of suspension. At the same time, glycogen level in equally slow and fast fibers of m. soleus and fast fibers anterior tibial muscle decreased substantially after 3 days of suspension but returned to baseline value by day 14. These changes are likely to be linked with altered activity of the muscles and hormonal factor.