骨芽細胞UMR106-01の5α-reductase活性に対するestradiolの影響  [in Japanese] Effect of Estradiol on 5α-reductase Activity in Osteoblast-like Cell (UMR106-01)  [in Japanese]

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Abstract

Bone is known to be a target organ of not only estrogens, but also androgens. The mechanism by which these steroids exert their action on bone cells is still poorly understood. In the present study, the effect of 17β-estradiol (E<SUB>2</SUB>) on 5α-reductase activity, converting testosterone (T) to a more potent biological androgen, dihy-drotestosterone (DHT), was assessed in an osteoblast-like cell line of rat origin (UMR106-01). Cells were incubated under standardized conditions with varying concentrations of E<SUB>2</SUB> (10<SUP>-12</SUP>-10<SUP>-6</SUP>M) for 48 hours. Incubation medium was replaced when the cells were preconfluent and thereafter at 24 hour intervals. Then the cells were harvested. Each cell homogenate was incubated with [4-<SUP>14</SUP>C]-T. DHT was detected as a single metabolite on silicagel thin layer chromatography. 5α-reductase activity was determined by measuring the amount of labeled DHT from T. The radiochemical purity of DHT recovered after incubation was confirmed by recrystallization to constant specific activity. Under the conditions used, no estrogen was detected. Production of insuline-like growth factor-I and alkaline phosphatase in UMR106-01 was increased when E<SUB>2</SUB> was added into the culture medium, however, 5α-reductase activity was significantly decreased by the addition of 10<SUP>-12</SUP>M to 10<SUP>-6</SUP>M of E<SUB>2</SUB>. Maximum inhibition was noticed at 10<SUP>-10</SUP>M. Our results demonstrate that UMR106-01 cells have a capacity to transform T into the biologically more potent androgen, DHT. The result, that the enzyme activity was influenced by E<SUB>2</SUB>, suggests the regulatory mechanism of both sex steroids on the steroid metabolism in osteoblasts.

Journal

  • Folia Endocrinologica Japonica

    Folia Endocrinologica Japonica 71(5), 651-658, 1995-05-01

    The Japan Endocrine Society

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