[Effect of vibrostimulation on support zones of rat's feet, and support loading on titin N2A-isoform and T2-fragment in m. soleus under the conditions of simulated microgravity].

Effects of daily 3-hr vibrostimulation of foot support zone and 3 hrs. of usual locomotion on titin N2A-isoform and proteolytic T2-fragment were studied in m. soleus of rats during 7-d suspension. Besides, effects of single one-hour support loading following 7-d weight-deprivation on titin N2A- and T2-forms were also evaluated in the muscle. Relative N2A content in m. soleus of the suspended group was noted to reduce approximately 25% as compared with the group of control. In the meantime, relative T2 content grew 2-3 times. Along with other changes in the muscle apparatus, N2A reduction contributes to the decline of m. soleus contractility in suspended rats, and development of the "hypogravity muscular syndrome" The daily 3-hr vibrostimulation of the foot support zones substantially (almost twice) decreased N2A disintegration with parallel reduction in approximately 1.5 times relative T2 content comparing with the Suspension group. Three hours of locomotion a day during suspension did not appear to decrease the relative N2A content in m. soleus. However, in this group of animals the relative T2 content in m. soleus was twice as high as in the control. Single-time presentation of support load for one hour soon after 7-d suspension resulted in more significant (approximately 30%) reduction in relative N2A content and twofold fall of relative T2 content as compared with m. soleus of the rats in group Suspension. These data attest to the leading role of support stimulation in maintaining the structural and functional properties of the musculoskeletal system, specifically the titin N2A-isoform content in m. soleus of rat deprived of gravitational loading. Besides, it was also shown that tracking changes in titin makes possible to follow the course of hypogravitational muscle syndrome and to evaluate effectiveness of preventive methods.