Intermittent hyperthermia enhances skeletal muscle regrowth and attenuates oxidative damage following reloading

Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida Submitted 27 June 2006 ; accepted in final form 10 November 2006 Skeletal muscle reloading following disuse is characterized by profound oxidative damage. This study tested the hypothesis that intermittent hyperthermia during reloading attenuates oxidative damage and augments skeletal muscle regrowth following immobilization. Forty animals were randomly divided into four groups: control (Con), immobilized (Im), reloaded (RC), and reloaded and heated (RH). All groups but Con were immobilized for 7 days. Animals in the RC and RH groups were then reloaded for 7 days with (RH) or without (RC) hyperthermia (41–41.5°C for 30 min on alternating days) during reloading. Heating resulted in 25% elevation in heat shock protein expression ( P < 0.05) and an 30% greater soleus regrowth ( P < 0.05) in RH compared with RC. Furthermore, oxidant damage was lower in the RH group compared with RC because nitrotyrosine and 4-hydroxy-2-nonenol were returned to near baseline when heating was combined with reloading. Reduced oxidant damage was independent of antioxidant enzymes (manganese superoxide dismutase, copper-zinc superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase). In summary, these data suggest that intermittent hyperthermia during reloading attenuates oxidative stress and improves the rate of skeletal muscle regrowth during reloading after immobilization. oxidant stress; heat shock proteins; antioxidant Address for reprint requests and other correspondence: S. L. Dodd, Dept. of Applied Physiology and Kinesiology, Univ. of Florida, Box 118206, Gainesville, FL 32611 (e-mail: sdodd{at}hhp.ufl.edu )