Subcellular distribution of [3H]oestradiol-17β and salt resistance of nuclear oestrogen complexes in the rat uterus after in-vivo administration of [3H]oestradiol-17β

Abstract

ABSTRACT The distribution of injected [3H]oestradiol-17β into nuclear and post-nuclear fractions as well as resistance to KCl (0·6 mol/l) extraction of nuclear oestrogen-binding sites in the rat uterus were studied. Both ovariectomized untreated and oestrogen-treated rats were used. One hour after injection of [3H]oestradiol into ovariectomized rats, 373 and 195 fmol/100 mg uterus were recovered in the nuclear and post-nuclear fractions respectively. About 17% of the nuclear-associated [3H]oestradiol was resistant to KCl extraction. After 18 h, the amount of [3H]oestradiol decreased to about 30% of that found after 1 h, and about 23% of nuclear complex remained resistant to extraction. In cardiac tissue, practically no [3H]oestradiol accumulated in the nuclear fractions and the amount recovered in post-nuclear fractions was about one-third of that in the uterine post-nuclear fractions. In the ovariectomized oestrogen-treated rats the distribution of [3H]oestradiol in nuclear and post-nuclear fractions was very similar and the proportion of the total nuclear fraction inextractable by KCl slightly higher (26%) than in untreated rats. After 18 h, while measurable amounts of [3H]oestradiol were found in post-nuclear fractions, no radioactivity was detected in the nuclear fraction. The results demonstrate the existence of salt-resistant nuclear oestrogen-binding sites in the mature ovariectomized rat uterus in vivo. Further, oestrogenization of ovariectomized rats did not significantly influence the amount or proportion of salt-resistant nuclear sites. J. Endocr. (1987) 113, 333–337