title: Osteoblast cells (MG-63 and HOS) have aromatase and 5 alpha-reductase activities.
abstract: Both aromatase and 5 alpha-reductase activities were found by whole-cell assay in osteoblast-like cells, MG-63 and HOS. Aromatase activity was measured by the [3H] water release method, and the formation of 5 alpha-androstanedione from androstenedione was expressed as 5 alpha-reductase activity. When CGS16949A, an inhibitor of aromatase, was added to the incubation medium at a concentration of 2 x 10(-9) M, sufficient to completely inhibit placental aromatase activity, only 63% to 68% inhibitions were observed. When progesterone, a competitive inhibitor of 5 alpha-reductase, was added at a concentration of 10(-5) M, 28% to 40% inhibitions were recorded. Because the release of [3H] from [1 beta-3H] androstenedione into water by 5 alpha-reductase is reported, results from the present study suggest that the measurement of aromatase activity in osteoblasts by the [2H] water release method may overestimate aromatase activity owing to the inclusion of 5 alpha-reductase activity. The results also suggest that osteoblast cells may play an important role in bone metabolism by transforming androgens into estrogens and more biologically active androgen derivatives.
authors.affiliation: Department of Obstetrics and Gynecology, Showa University School of Medicine, Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Shimodaira
authors.forename: H
authors.initials: H
authors.lastname: Fujikawa
authors.forename: F
authors.initials: F
authors.lastname: Okura
authors.forename: Y
authors.initials: Y
authors.lastname: Shimizu
authors.forename: H
authors.initials: H
authors.lastname: Saito
authors.forename: T
authors.initials: T
authors.lastname: Yanaihara
mesh_terms: D000818:Animals; D001141:Aromatase / Q000378:metabolism*; D047072:Aromatase Inhibitors; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017316:Fadrozole / Q000494:pharmacology; D006801:Humans; D010006:Osteoblasts / Q000166:cytology / Q000201:enzymology*; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011374:Progesterone / Q000494:pharmacology; D051381:Rats; D014316:Tritium
chemical_list: D047072:Aromatase Inhibitors; D004791:Enzyme Inhibitors; D014316:Tritium; D011374:Progesterone; D010088:Oxidoreductases; D001141:Aromatase; D017316:Fadrozole