RESUMO
This study investigated the time course of changes in heat shock protein (HSP) 72, muscle weight and cross-sectional area of muscle fibers after injection of bupivacaine (BPVC) into the soleus muscle. Adult male Wistar rats (n=36) were anesthetized by pentobarvital sodium and 0.5 ml of BPVC was injected into the left soleus muscle, whereas the contralateral right soleus muscle was served as the control. Bilateral soleus muscles were dissected at 1, 2, or 4 days or 1, 2, or 4 weeks after the injection. Muscle fibers were disrupted at days 1-2 after BPVC injection and regenerated fibers that have centrally located nuclei in cytoplasm appeared 4 days after the injection. The cross-sectional area of regenerated fibers gradually increased during 4 days-4 weeks after the injection. The soleus muscle weight decreased until 1 week after the injection, then gradually increased during 1-4 weeks of recovery. The content of HSP 72 was drastically decreased in the soleus muscle 1 day after BPVC injection (p<0.01), then gradually increased during 2 days-4 weeks of recovery, and returned to the control level at 4 weeks of recovery. A similar time course of change was observed for the cross-sectional area of the regenerating fibers and HSP 72 expression. These results suggest that the BPVC injection induces disruption of muscle fibers and degradation of HSP 72, however, regeneration of muscle fibers indicated by increases in cross-sectional area occurs with increases in HSP 72 content during 4 weeks of recovery period.
RESUMO
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 1 h 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 1 h by raising the air temperature inside the steel can to 54-58t with a flexible heater so as to bring the muscle temperature up to 42°C. 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 1 h of heat stress. In the soleus muscle, all of the HSP levels analyzed were significantly increased during 0-4 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 1 h 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.
RESUMO
To determine whether fiber type-specific expression of heat shock protein (HSP, or stress protein) occurs in unstressed rat skeletal muscle, the medial gastrocnemius of adult female Sprague-Dawley rats was subjected to immunohistochemical analysis. Antibodies against 5 types of anti-myosin heavy chain (MHC) were used to classify the type of fibers, and 2 types of anti-HSP antibodies were employed to analyze the fiber type-specific expression.<BR>Serial cross-sections of 10 μm thick cut by a cryostat were incubated with primary anti-MHC or anti-HSP 60 and 72 antibodies, followed by biotinylated secondary anti-mouse antibodies, and avidin-biotin complex solution. A peroxidase DAB substrate kit (Vector SK-4100) or BCIP/NBT solution was used to visualize the immunoreaction of each fiber type.<BR>By using the 5 types of anti-MHC antibodies, fibers were classified into 4 types : slow-type I, fasttypes IIA, IIX, and IIB. Anti-HSP 72 antibody reacted with many, but not all, type I and IIA fibers, whereas anti-HSP 60 antibody reacted specifically with type I fibers. Neither type IIX nor IIB fibers showed immunoreactivity with anti-HSP 60 or 72 antibodies. These results suggest that the expression of HSP 60 protein is related to that of type I MHC, and that the expression of HSP 72 protein may be related to that of types I and ha MHC, in unstressed rat skeletal muscle.