Human Osteoblast‐Like Cells Contain Specific, Saturable, High‐Affinity Glucocorticoid, Androgen, Estrogen, and 1α,—Dihydroxycholecalciferol Receptors

Abstract

ABSTRACT: Glucocorticoids, androgens, estrogens and 1α,25‐dihydroxycholecalciferol (1α,25‐(OH)2D3) exert a variety of effects on bone homeostasis. We have measured the receptors for these hormones in cultured human osteoblast‐like cells. Specific binding was found with each of the four steroids tested, namely maximum binding capacities, Bmax, of 2,581 (1,368–4,223), 146 (101–237), 176 (20–552), and 387 (290–620) fmol mg DNA−1 (mean, range) for [3H]dexamethasone, [3H]5α‐dihydrotestosterone, [3H]17β‐estradiol ([3H]E2), and [3H]1α,25‐(OH)2D3, respectively. The corresponding apparent dissociation constants were 13.3 (9.2–22.2), 0.43 (0.23–0.94), 0.45 (0.17–0.88), and 0.020 (0.008–0.030) nM, respectively. Both high‐affinity, low‐capacity and low‐affinity, high‐capacity specific [3H]E2 binding were demonstrable. In conclusion, we could demonstrate that human osteoblast‐like cells contain specific glucocorticoid receptors. In addition specific androgen, estrogen, and 1α,25‐(OH)2D3 binding was demonstrated. These cells contain several times more binding sites for dexamethasone than for dihydrotestosterone, estradiol, and 1α,25‐(OH)2D3, a feature that might contribute to the marked sensitivity of human bone to glucocorticoids.