Endocrinology, Vol 115, 1197-1202, Copyright © 1984 by Endocrine Society

ARTICLES

Estrogen modulation of nuclear matrix-associated steroid hormone binding

RC Simmen, AR Means and JH Clark

Estrogen regulation of the intranuclear distribution of estrogen- binding proteins has been examined in the chicken liver. Administration of estrogen [diethylstilbestrol (DES)] resulted in a rapid, dose- dependent increase in two types of estrogen-binding sites associated with the nuclear matrix. Type I appeared to be the estrogen receptor (ER; Kd for estradiol = 2.0 nM), whereas type II was equivalent to binding sites previously defined in rat uterine nuclei (Kd = 15 nM). The association of nuclear ER and type II sites with the nuclear matrix followed a time course corresponding to the maximal accumulation of nuclear ER in the liver. A 2-fold enrichment (per U protein) of nuclear ER in the matrix was obtained at a dose of 20 micrograms DES/0.2 kg compared to control values. Further enrichment was observed with higher doses of DES (200 and 2000 micrograms). The antiestrogens tamoxifen (tamoxifen-citrate) and zuclomiphine 2-[p-(chloro-1,2-diphenyl- vinyl)phenoxyl]citrate) were potent inhibitors (greater than or equal to 50%) of the estrogen-stimulated association of both ER and type II sites with the matrix. However, they did not increase total nuclear or matrix ER concentrations when administered alone. These data demonstrate that the association of ER with liver nuclear matrix is estrogen dependent and suggest that the biological effects of estrogen at the nuclear level may be mediated by this association.