Role of estrogen receptor binding and transcriptional activity in the stimulation of hyperestrogenism and nuclear bodies.

Abstract

The The nonsteroidal estrogen antagonist nafoxidine is an atypical long-acting estrogen in the immature rat. An injection of nafoxidine causes the translocation of the estrogen receptor from the cytoplasm to the nucleus of uterine cells with a subsequent long-term nuclear retention of the receptor, presumably as a receptor-nafoxidine complex. This long-term nuclear retention of the receptor is accompanied by sustained stimulation of uterine size and long-term increase of nuclear RNA polymerase activities (1-5). A single injection of the physiological hormone 17,B-estradiol also results in nuclear retention of the receptor, stimulation of uterine hypertrophy, and increase of nuclear RNA polymerase activities but these effects are of a much shorter duration than those observed after nafoxidine administration (1-7). It has recently been shown that a single injection of nafoxidine or Clomid, a closely related compound, in neonatal rats causes hyperestrogenization of the reproductive tract which results in the appearance of multiple abnormalities and tumors in the adult animal (8).To relate and extend the above biochemical and histopathological observations to morphological changes that occur in the normal immature rat uterus in response to nafoxidine and estradiol treatment, we examined the ultrastructure of uterine luminal epithelial cells as well as changes in nuclear RNA polymerase activities after long-term exposure to these compounds. Estradiol was dissolved in 0.9% NaCl/1% ethanol, and nafoxidine was dissolved 1% ethanol in distilled water. Alternatively, 50-mg paraffin implants were prepared containing 10% (wt/wt) estradiol by liquifying a known quantity of paraffin, mixing the appropriate quantity of hormone with it, and dropping a uniform volume of the liquid mixture onto a precooled glass surface (9). Vehicle (0.25 ml), estradiol (1.0 Ag), or nafoxidine (50,ug) was administered subcutaneously at various times prior to sacrifice. In experiments involving implants, animals were placed under light ether anesthesia, a small incision was made in the nape of the neck, a paraffin implant was placed subcutaneously, and the incision was closed with one or two sutures. MATERIALS AND METHODSAnimals were sacrificed by cervical dislocation. The uteri were rapidly removed, stripped of adhering fat, weighed, and placed in either ice-cold 0.9% NaCl/5 mM ethylene glycolbis(fi-aminoethyl ether)-N,N'-tetraacetic acid for nuclear isolation or in the appropriate fixative for morphological examination (see below).Isolation of Nuclei. Nuclei were isolated by a modification of the hexylene glycol procedure as described (5).Assay of Endogenous RNA Polymerase Activities. Total endogenous nuclear RNA polymerase activities were measured by the addition of an aliquot of nuclei g of DNA) to a tube that contained 2. (12)(13)(14)(15)(16) Ci/ mmol) in a final volume of 50 ,l. a-Amanitin was used to determine the amount of activity due to RNA polymerase II. RNA polymerase I activity was determined by subtraction of the a-amanit...

Endocrine Consequences of Continuous Antiestrogen Therapy with Tamoxifen in Premenopausal Women

“…In contrast to 17,8-estradiol, the method of trapezoids. The antiestrogen-receptor complex exhibited long-term ts were done on days 9-12 nuclear retention, resulting in early estrogen-like rentrol cycle when serum E 1 ys -1 ohen tarmoEn sponses and later antagonism of estrogen action (12). plasmic estrogen receptor (11), a postulate that is the subject of some controversy (13).…”

Nuclear bodies as structural indicators of estrogenic stimulation in uterine luminal epithelial cells

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Preliminary evidence has indicated that the number of nuclear bodies in uterine luminal epithelial cells of the immature rat may be related to the duration of nuclear retention of the estrogen receptor complex (Clark et al, 1978). To test this hypothesis, an ultrastructural analysis of nuclear and cytoplasmic differentiation was performed at 4,12,24,48, and 72 hr after a single injection of estradiol or nafoxidine (synthetic estrogen agonistlantagonist) int0 21 day female rats.

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Ultrastructural modifications provoked by tamoxifen either alone or combined with oestradiol in the uteri of fetal or newborn guinea-pigs

“…Very limited information is available concerning the action of antioestrogenic compounds derived from triphenylethylene on the ultrastructure. Clark, Hardin, Padykula & Csordas (1978) observed the for¬ mation of nuclear bodies in the epithelial cells of the uterus of immature rats after 3 days of treatment with nafoxidine and, also in the rat, Holinka, Bressler, Zehr & Gurpide (1980) observed a limited cell degeneration after 3 days of treatment with tamoxifen. However, the alterations observed in the present work are much more dramatic, particularly with the formation of numerous secretory granules, indicating an intense activity of tamoxifen.…”