EFFECT OF HEAT STRESS ON DESMIN EXPRESSION IN ATROPHIED SOLEUS MUSCLE

In the present study, we investigated the effect of heat stress on disuse atrophy from changes in the muscle protein levels of desmin and calpain. Wistar strain female rats (6-8 months old) were randomly assigned to two experimental groups: control (C) and heat stress (H). One hindlimb of all animals was immobilized in plantar flexion with plaster. Before immobilization, animals in H group were placed in a heat chamber (42°C for 60 min). Following 6 days of immobilization, the soleus muscles were removed and analyzed. Although immobilization resulted in significant muscle atrophy in all experimental animals, the soleus weight-to-body weight ratio in immobilized limbs of H group was significantly higher compared to that of C group. Expression of desmin and HSP72 in the atrophied soleus muscle from C group was significantly lower compared with the contralateral muscle; but this was not the case in H group. Further, in C group, the ratio of autolyzed calpains I increased significantly in the atrophied muscle compared to the contralateral muscle. These results show that the effect of heat stress on disuse skeletal muscle atrophy is attributed to the decreasing degradation of desmin by suppressing the activation of calpain.