Low-intensity treadmill exercise enhances fast recovery from bupivacaine-induced muscle injury in rats

BACKGROUND: Although bupivacaine has been used to study muscle degeneration and regeneration, the potential enhancement of muscle injury by exercise has not been well examined. The purpose of this study was to determine whether low-intensity treadmill exercise enhances fast recovery from bupivacaine-induced muscle injury and to examine concomitant changes in heat-shock protein 70 (HSP70) expression during regeneration process. METHODS: In this study, Sprague-Dawley rats were randomly divided into the following four groups: the control group (CON), the sham group (SHAM), the injury group (INJ), and the injury and exercise group (EX) (n = 14 in each group). Expressions of HSP70, inducible nitric oxide synthase (iNOS), and caspase-3 were determined at 1 and 7 days after bupivacaine-induced muscle injury in gastrocnemius. RESULTS: Results showed that bupivacaine-induced muscle injury (1 day) significantly increased the expressions of HSP70 and iNOS. At 7 days after the muscle injury, HSP70 expression was higher in the EX group compared with that in the INJ group and elevated level of HSP70 by exercise is concomitant with downregulation of iNOS and the decreased number of caspase-3-positive cells as a marker of apoptosis. Fewer necrosis of myofibers were also found in the EX group compared with the INJ group. CONCLUSION: Our results suggest that low-intensity treadmill exercise may enhance fast recovery from bupivacaine-induced muscle injury in rat partly by HSP70 upregulation.