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Interaction between cell nuclei and the complexes of estradiol (E2) with uterine cytosol estrogen receptors (ER) or with different forms of female and male rat liver cytosol ER was studied and compared. The complexes of E2 with forms I and II of liver ER are capable to translocate to the cell nuclei similarly to E2 receptor complexes of the uterus. The complexes of E2 with an unusual male rat liver estrogen-binding protein do not bind to the nuclei. The processes of translocation of the complexes of E2 with form I of liver ER and uterine receptors have some features in common. In the conditions of low ionic strength media, the complexes of E2 with forms I and II of liver ER manifest differences in the kinetics and level of translocation into the cell nuclei. The differences disappearing with ionic strength increase. The differences disappearing with ionic strength increase. It is suggested that the different forms of liver ER participate in the realization of E2 multiple effects in the liver.

The aim of the present investigation was to discover whethertranslocation of rat liver cytosol ER takes place into the cell nucleus after injection of various doses of the hormone in vivo, and, if it does, to study the principles governing the dynamics of ER in the hepatocytes at various time intervals after injection of the hormone. A comparative analysis also was made of changes in the ER level in the hepatocytes on changes on the endocrine status of the animal. Estrogen receptors in the cytosol (CR) were determined by incubating samples with 7.5 nM (2,4,6,7-/sup 3/H)-E/sub 2/ (specific radioactivity 90-100 Ci/mmole) in the absence or in the presence of a 200-fold excess of unlabeled E/sub 2/ in the course of 3 h at 0-4/sup 0/C. Nuclear estrogen receptors (NR) were determined in a 0.4 M NaCl extract of nuclei.