[Dynamics of rat's soleus muscle recovery from the suspension-induced atrophy]

Dynamics of the 60-d soleus recovery was studied morphologically and histomorphometrically in female rats exposed to 30-d tail-suspension. Suspension led to soleus atrophy manifested by substantial losses in mass (56% vs. the control) and cross-sectional area of myofibers, and partial transformation of slow fibers into fast. The most intensive recovery processes in the soleus, reverse to the atrophic ones, were observed in the period between days 2 and 8 of readaptation, but then they subsided. Full recovery of the soleus mass and CSA took approximately 60 days of readaptation. Fast myofibers are less susceptible to atrophy and, therefore, recovered sooner than the slow ones. Percentage of slow-to-fast fibers returned to the norm between days 14 and 30. In addition to the persisting atrophy on readaptation day 2, there were some hemodynamic disorders in the soleus fraught with interstitial edema, distortion of muscle trophism, dystrophic developments in muscle fibers, and death of a number of fibers. Edema faded away between days 8 and 14 of readaptation. Recovery of the soleus muscle was considerably compromised by hemodynamic disorders at the beginning of readaptation.