Changes in the skeletal expression levels of stress proteins in rat muscles due to heat stress exposure

The expression levels of heat shock proteins after heat stress on rat slow soleus and fast plantaris muscles were examined and compared during a recovery period following 1h of heat stress. The left hindlimbs of adult male Wistar rats (n = 15) were carefully inserted into a stainless steel can and subjected to heat stress for Ih by raising the air temperature inside the steel can to 54 similar to 58 degreesC with a flexible heater so as to bring the muscle temperature up to 42 degreesC. The muscles of the contralateral right hindlimb served as the control. The expression levels of HSP 60, HSP 72, and HSC 73 were analyzed by Western blotting after 0, 2, and 4 h of recovery following Ih of heat stress. In the soleus muscle, all of the HSP levels analyzed were significantly increased during 0 similar to 4 h of recovery. On the other hand, heat stress had no effect on the expression levels of HSPs, except HSP 60, in the plantaris muscle during recovery after Ih of heat stress. These results suggest that the slow soleus muscle has a higher ablility to respond quickly to heat stress than the fast plantaris muscle.