Intranuclear transformation of the estrogen receptor in adulthood: tissue and species similarities.

Previous studies in immature rodents have demonstrated the presence of two forms (4S, 5S) of salt extractable estrogen receptor in uterine nuclear preparations. The link between these binding forms appears to be that of hormone dependence and time in a precursor-product relationship. In the present study, this relationship has been observed in nuclear extracts of the uterus and anterior pituitary of intact and gonadectomized adult rats. Both forms of the estrogen receptor have also been isolated from purified nuclei of endometrial cell preparations of the adult dog. As a result of these studies, the phenomenon of intranuclear receptor transformation in estrogen action may now be extended to include (a) the physiologic state of adulthood, (b) persist in the absence of endogenous estrogens and (c) be a feature of estrogen target tissues in animal species other than rodents.