Estrogen Administration Attenuates Immobilization-Induced Skeletal Muscle Atrophy in Male Rats

抄録

We tested the hypothesis that estrogen administration would retard immobilization-induced muscle atrophy in adult male rats. Rats were injected for 24 days with either estrogen (40 µg/kg⁻¹, β-estradiol 3-benzoate in olive oil vehicle) or vehicle alone. At day 14 of estrogen treatment, the hindlimb muscles of one leg were immobilized in plantar flexion position using a plaster cast. Following 10 days of immobilzation, both the atrophic and the contralateral soleus muscles were removed and analyzed to determine the level of muscle atrophy along with measurement of the protein levels of CuZn-superoxide dismutase (CuZnSOD), heat shock protein 72 (HSP72), and selected proteases. Compared to placebo animals, estrogen treatment significantly reduced (–35%) muscle atrophy. Further, estrogen significantly abridged the expression of the calcium-activated protease, calpain in the atrophied hindlimb muscle. In contrast, estrogen treatment did not alter protein levels of HSP72 in the immobilized soleus muscle. These results support the postulate that estrogen attenuates the rate of disuse muscle atrophy, due in part, to reductions in immobilization-induced calcium-activated protease levels.