Recently many studies have reported the relationship between muscle fiber phenotype or size and heat shock protein (HSP) 72 or calcineurin (CaN) in mammalian skeletal muscles. In this study, changes of the expression levels of HSP72 and CaN proteins were analyzed in atrophied soleus and hypertrophied plantaris muscles. Male Wistar rats were used for two models of experiment: 1) left hindlimb was immobilized for two weeks, and 2) synergistic soleus and gastrocnemius were ablated and the remained plantaris was hypertrophied for two weeks. In atrophied soleus muscle, the phenotype of myosin heavy chain (MHC) isoform was shifted toward fast type, and the contents of HSP72 and CaN proteins were decreased. In contrast, MHC isoforms were shifted toward slower phenotype and the protein levels of HSP72 and CaN were increased in hypertrophied plantaris muscle. These results may suggest the contribution of HSP72 and CaN to the changes of muscle size and/or fiber phenotype, although additional studies are needed to clarify the roles of these proteins.

DESCENTE SPORTS SCIENCE Vol.26/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE