Effects of tamoxifen, stilbestrol and metyrapone on binding of various steroids to cytosol receptors in human breast cancer cytosols
Konishi, Y.
Kobe Journal of Medical Sciences 27(3): 103-112
1981
ISSN/ISBN: 0023-2513 PMID: 7265820 Document Number: 169213
The influences of metyrapone, tamoxifen and stilbestrol on steroid receptors in breast cancer tissues were studied in an attempt to elucidate their mode of action. Estradiol (E), dexamethasone, cortisol, dihydrotestosterone, synthesized progesterone (R-5020) and synthesized dihydrotestosterone (R-1881) were used. The supernatant from cancer tissues was incubated with 3H-steroid hormones in the presence or absence of unlabeled steroids, stilbestrol, metyrapone or tamoxifen. Hormone-receptor complexes were isolated and the radioactivity measured. Tamoxifen inhibited the binding of E, R-1881, R-5020 and dexamethasone (DX) to the corresponding receptors; the binding capacities of serum for steroid hormones were also reduced. Tamoxifen had more potent inhibitory effect on binding of endogenous substances in blood and in cells to their receptors. The inhibitory effect shared by tamoxifen, stilbestrol and metyrapone despite their widely divergent chemical structures and the apparent specificity of steroid-receptor binding reactions suggest that the receptors for the said hormones are identical in molecular structure or, at least, that their receptors have a certain reactive group or moiety in common.