The response of apoptotic and proteolytic systems to repeated heat stress in atrophied rat skeletal muscle.
We examined the effect of repeated heat stress on muscle atrophy, and apoptotic and proteolytic regulation in unloaded rat slow- and fast-type skeletal muscles. Forty male Wistar rats (11 week-old) were divided into control (CT), hindlimb unweighting (HU), intermittent weight-bearing during HU (HU + IWB), and intermittent weight-bearing with heat stress during HU (41-41.5°C for 30 min; HU + IWB + HS) groups. The HU + IWB + HS and HU + IWB groups were released from unloading for 1 h every second day, during which the HU + IWB + HS group underwent the heating. Our results revealed that repeated bouts of heat stress resulted in protection against disuse muscle atrophy in both soleus and plantaris muscles. This heat stress-induced protection against disuse-induced muscular atrophy may be partially due to reduced apoptotic activation in both muscles, and decreased ubiquitination in only the soleus muscle. We concluded that repeated heat stress attenuated skeletal muscle atrophy via suppressing apoptosis but the response to proteolytic systems depend on the muscle phenotype.
Graduate School of Health and Sports Science, Juntendo University, Inzai, Chiba, Japan t-yoshih@juntendo.ac.jp.
Toshinori
T
Yoshihara
Faculty of Education, Yamaguchi University, Yoshida, Yamaguchi, Japan.
Takao
T
Sugiura
Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Yuki
Y
Yamamoto
Graduate School of Frontier Biosciences, Osaka University, Toyonaka, Osaka, Japan.
Tsubasa
T
Shibaguchi
Faculty of Medicine, Juntendo University, Bunkyo-ku, Tokyo, Japan.
Ryo
R
Kakigi
Graduate School of Health and Sports Science, Juntendo University, Inzai, Chiba, Japan.
Hisashi
H
Naito
Apoptosis; disuse muscle atrophy; heat shock protein; protein degradation