Effects of heat shock protein and calcineurin in hypertrophied and atrophied skeletal muscles

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During passed two years, I investigated the effects of heat shock proteins (HSP) and calcineurin (CaN) in hypertrophied or atrophied rat skeletal muscles. In clenbuterol injected rat hindlimb muscles, which occurred hypertrophy and the shift of fiber phenotype from slow-to-fast, Hsp72 was decreased in the slow soleus muscle, where the CaN was increased. Functionally overload (FO) of fast plantaris muscle by cutting the tendons of its synergists induced muscle fiber hypertrophy and the shift of fiber phenotype from fast-to-slow. Hsp72 was also upregulated in functionally overloaded plantaris concomitantly with the increase in fiber size and slow fiber phenotype. Muscle hypertrophy and the shift of fiber phenotype observed in the FO plantaris was inhibited by the treatment of cyclosporin A, a inhibitor of CaN, indicating that the CaN was related to the fiber size and phenotype. In addition, thyroid hormone (T3) treatment to the FO plantaris downregulated to the expression level of the Hsp72 and CaN.