Identification of androgen receptors in normal human osteoblast-like cells.
The sex steroids, androgens and estrogens, are major regulators of bone metabolism. However, whether these hormones act on bone cells through direct or indirect mechanisms has remained unclear. A nuclear binding assay recently used to demonstrate estrogen receptors in bone [Eriksen, E.F., Colvard, D.S., Berg, N.J., Graham, M.L., Mann, K.G., Spelsberg, T.C. & Riggs, B.L. (1988) Science 241, 84-86] was used to identify specific nuclear binding of a tritiated synthetic androgen, [3H]R1881 (methyltrienolone), in 21 of 25 (84%) human osteoblast-like cell strains and a concentration of bound steroid receptors of 821 +/- 140 (mean +/- SEM) molecules per cell nucleus. Binding was saturable and steroid-specific. Androgen receptor gene expression in osteoblasts was confirmed by RNA blot analysis. Relative concentrations of androgen and estrogen receptors were compared by measuring specific nuclear estrogen binding. Nuclear binding of [3H]estradiol was observed in 27 of 30 (90%) cell strains; the concentration of bound estradiol receptor was 1537 +/- 221 molecules per cell nucleus. The concentrations of nuclear binding sites were similar in males and females for both [3H]R1881 and [3H]estradiol. We conclude that both androgens and estrogens act directly on human bone cells through their respective receptor-mediated mechanisms.
Colvard
D S
DS
Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905.
Eriksen
E F
EF
Keeting
P E
PE
Wilson
E M
EM
Lubahn
D B
DB
French
F S
FS
Riggs
B L
BL
Spelsberg
T C
TC
D001667:Binding, Competitive; D015152:Blotting, Northern; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D006801:Humans; D007700:Kinetics; D009693:Nucleic Acid Hybridization; D010006:Osteoblasts / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000302:isolation & purification; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000378:metabolism
D012333:RNA, Messenger; D011944:Receptors, Androgen; D011960:Receptors, Estrogen