Osteoblast cells (MG-63 and HOS) have aromatase and 5 alpha-reductase activities.
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.
Shimodaira
K
K
Department of Obstetrics and Gynecology, Showa University School of Medicine, Tokyo, Japan.
Fujikawa
H
H
Okura
F
F
Shimizu
Y
Y
Saito
H
H
Yanaihara
T
T
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
D047072:Aromatase Inhibitors; D004791:Enzyme Inhibitors; D014316:Tritium; D011374:Progesterone; D010088:Oxidoreductases; D001141:Aromatase; D017316:Fadrozole