Abstract
To investigate the effect of unilateral cast immobilization, one hindlimb of rats was immobilized for 2 weeks by a cast and remobilization was carried out for up to 4 weeks. Rats were sacrificed at the start of immobilization, after 2 weeks of immobilization and after 1, 2, 3 and 4 weeks of resumed normal activity following cast removal. After euthanasia with ether, the gastrocnemius, soleus, and tibialis anterior muscles as well as the bones of their proximal attachments were removed. Cryosections were used for hematoxylin-eosin staining and ATPase activity. Two weeks of immobilization resulted in a significant decrease of wet weight of muscles and reduction of muscle fiber cross-sectional area. Relative incidence of Type II fibers increased in the soleus and gastrocnemius muscle after two weeks of immobilization and bone weights decreased. After remobilization, muscle atrophy due to immobilization gradually reversed. However, some atrophy still remained 4 weeks after cast removal. The immobilization caused severe atrophy in the leg, with complete recovery requiring much more time than the period of immobilization. This suggests a need to investigate interventions to facilitate the recovery of atrophied tissues.
