Abstract
Dexamethasone at concentrations of 1.5 × 10-8 M and higher inhibited the incorporation of [14C]-proline into proline and hydroxyproline-containing protein fractions of freshly-isolated bone cells. Amino acid incorporation was only partially blocked by 1.5 × 10-8 M dexamethasone after a 5 h incubation, although incorporation could be completely blocked with puromycin. Parathyroid hormone enhanced [14C]-proline incorporation into total protein after a 3 h incubation, an effect which was abolished by simultaneous treatment with dexamethasone. Other steroids and vitamin A were tested alone and in combination with dexamethasone to determine whether the effects of these agents on bone cell protein synthesis reflected their affinities for bone cytosol binding sites previously demonstrated. At the concentrations tested, progesterone, the spirolactone SC-26304 and vitamin A all inhibited incorporation; cortexolone and estradiol did not. Cortexolone, progesterone and SC-26304 reversed the inhibitory effects of dexamethasone. These results are consistent with the earlier binding studies, and suggest that the effects of glucocorticoids on bone cell protein synthesis are mediated by cytosol receptors.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 265-271 |
| Number of pages | 7 |
| Journal | Journal of Steroid Biochemistry |
| Volume | 9 |
| Issue number | 3 |
| DOIs | |
| State | Published - Mar 1978 |
Funding
The mechanism of action of glucocorticoids, as for all steroid hormones, is postulated to require initial binding of the hormone to specific receptors in the cytoplasm of target tissue [l]. We have previously demonstrated the presence of glucocorticoid binding proteins in bone cells prepared from fetal rat calvaria [2]. These binding sites have now been further characterized as receptors for hormone action, based upon the observation that they mediate transfer of the hormone to the nucleus [3]. Such isolated bone cells have previously proven useful in studies of bone metabolism, and provide a system in which glucocorticoid induced physiological functions can be correlated with glucocorticoid receptor binding. In the present study, employing freshly isolated bone cells and dexa-methasonet as the glucocorticoid, we confirm the earlier results of Peck, et al. which demonstrated that Supported by NIH research grants AM 11262 and AM 18156 and NIH Research Career Development Award 5K04 AM 70210 (to P. Stern). * Present address: Institute for Biomedical Research, The University of Texas at Austin, Austin TX 78712, U.S.A. f The following abbreviations have been used: dexamethasone: 9-a-fluoro-ll/l,l7,21-trihydroxy-16x-methylpregna-1,4-diene-3,20-dione; cortexolone: 17,21-dihydroxy-4-pregnene-3,20-dione; SC-26304: 3-(3-oxo-7a-carboxyisopropyl-17/Ghydroxy-4-androstene-17a-yl) propionic acid y-lactone; HEPES: hydroxylethylpiperazone N’-2-ethanesulfonic acid; TCA: trichloroacetic acid; PPO: 2,5-diphenyloxazole; dimethyl-POPOP: 1,4-bis[2-(4-methyl-5-phenyloxazolyl)]-benzene; PTH: parathyroid hormone.
ASJC Scopus subject areas
- Endocrinology
- Biochemistry