The effect of various hormones on regucalcin mRNA expression in osteoblastic MC3T3-E1 cells in vitro was investigated. Cells with subconfluency were cultured for 24 or 48 h in a medium containing either vehicle or various hormones without fetal bovine serum. Regucalcin mRNA expression was significantly increased after culture with parathyroid hormone (synthetic human PTH; 10−7 M), insulin-like growth factor-I (IGF-I; 10−8 M), or 17β-estradiol (10−10 or 10−9 M) for 48 h. Culture with 1,25-dihydroxyvitamin D3 (10−7 M) for 48 h caused a significant decrease in regucalcin mRNA expression. Regucalcin mRNA expression was significantly decreased after culture with tumor necrosis factor-α (1 or 10 ng/ml of medium) for 24 or 48 h. The effect of PTH or IGF-I in increasing regucalcin mRNA expression was not seen in the presence of staurosporine (10−8 M), an inhibitor of protein kinase C, or PD98059 (10−7 M), an inhibitor of mitosis-activated protein kinase (MAP kinase), respectively, suggesting that regucalcin mRNA expression is enhanced through intracellular signaling factors. This study demonstrated that regucalcin mRNA expression in osteoblastic MC3T3-E1 cells is regulated by various hormones.

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