抄録
The biological effects of estrogen receptor(ER) had to be mediated by a receptor protein. The skeletal muscle is one of the important target tissues for estrogen, as evidenced by significant effects of estrogen on muscle contraction, muscle fatigue and cell proliferation. In this study, we investigated the regulation of ER expression by the immunoblot analysis. The ER in C2C12 cell was detected as 66 kDa and 54 kDa forms as well as in the ovary, uterus, skeletal muscle, kidney, lung, adipose in the intact mouse. Although the intensity of 66 kDa form was stronger than that of 54 kDa in intact mouse, 66 kDa form was weaker than 54 kDa form in C2C12. The effect of the 17-beta estradiol administration on the ER expression in C2C12 cell was investigated. The ER expression increased gradually after the 17-beta estradiol administration, then reaching the maximum at 12 h. This increase was compatible with the effect of proliferation and the alteration of intracellular Ca concentration. Therefore, these results suggest that the modulation of ER expression level by the extracellular situation, Ca concentration and the ligands, could be associated with the proliferation and the intracellular Ca concentration. The functional role of 66 kDa and 54 kDa forms in some tissues and cells will be clarified by another analysis. [Jpn J Physiol 54 Suppl:S117 (2004)]
