Rat uterine growth and induction of progesterone receptor without estrogen receptor translocation

The rat uterus responds to estradiol (E2) and E2 benzoate stimulation with an increase in progesterone receptor production and with growth. These responses were also elicited to varying degrees by a series of estrogenic (ICI 77,949 and ICI 47,699) and antiestrogenic triphenylethylene derivatives [tamoxifen (TAM), 4-hydroxy-TAM (4-OH-TAM), and 4-CH3-TAM]. These compounds have a range of affinities for the estrogen receptor (ER) and are able to compete with [3H]E2 binding in the uterus in vivo. Within 1-2 h of a sc injection of high affinity ligands (E2, E2B, and 4-OH-TAM), there was decrease in cytosol ER. This decrease was also observed with TAM, which is metabolized to 4-OH-TAM in vivo. In contrast, there was no decrease in cytosolic ER in animals treated with low affinity compounds (ICI 77,949, ICI 47,699, and 4-CH3-TAM) at any time before the onset of an estrogenic response. Furthermore, the nuclear ER increased after administration of a high affinity ligand (E2), as measured by exchange assay, but no increase in nuclear ER was observed after administration of low affinity ligands (ICI 77,949 and 4-CH3-TAM), although estrogenic responses were produced. From these data we have suggested a functional model to explain ER-mediated events in the rat uterus that supports the recent proposal that unoccupied ER is located in the nuclear compartment. In this model, the majority of unoccupied ER may reside in the nucleus in vivo; however, when the cells are disrupted in vitro, the unoccupied receptor or dissociation of low affinity ligand-ER complex causes unoccupied receptor to fall out of the nucleus and be incorporated into the cytosolic fraction. The high affinity ligand-ER complexes are retained in the nucleus. This would suggest that the apparent translocation of the ER from the cytoplasm to the nucleus may be an artifact. The data may reflect differential extraction of unoccupied receptors from the nucleus rather than transfer of receptor complexes to the nucleus.     

Estrogen receptors in rat bone: their interaction with estrogen receptor modulators.

Estrogen receptors (ER) were studied in rat bone cytosol using immunoprecipitation, and Western blot technique. Ligand specificity of bone ER was studied using various known modulators of ER. Competitive experiments were performed under exchange conditions in bone tissue obtained from one day old rats. ER alpha and beta subtypes were identified using immunoblotting experiments compared with that of ovarian and uterine tissues. In competitive binding assay, maximum inhibition in specific 3H-E2 binding was shown by E2 followed by tamoxifen and diethylstilbestrol. 7-Hydroxycentchroman and 85/287 also inhibited specific 3H-E2 binding but were less potent as compared to tamoxifen and diethylstilbestrol. However, 85/287 was less effective (81%) as compared to 7-hydroxycentchroman. Polyacrylamide gel electrophoresis of cytosol and Western blot analysis revealed the presence of 55 kD and 66 kD ER immunoreactive bands corresponding to alpha and beta subtypes, respectively, in bone as well as in uterus. Interestingly, the concentration of 55 kD ER was 3-fold higher than that of 66 kD ER. Ovarian cytosol revealed the presence of a 55 kD band only in Western blot analysis. These studies suggest the action of estrogens/ER modulators on osteoblasts which contain a limited number of classical alpha as well as beta sub types of ER that are known to be structurally different in their hormone-binding domains.     

Transdominant suppression of estrogen receptor signaling by progesterone receptor ligands in uterine leiomyoma cells

Uterine leiomyomas develop in reproductive-age women with high frequency and are dependent on the production of ovarian hormones. While it is generally accepted that these tumors are estrogen (E(2))-responsive, the role of progesterone (P(4)) in modulating tumor growth is less clear. In the present study, an in vivo/in vitro rat model was used to characterize progesterone receptor (PR) isoform expression in uterine leiomyoma and investigate PR signaling using progestins and antiprogestins in the leiomyoma-derived cell line ELT-3. PR-A was the predominant isoform expressed in normal myometrium, leiomyomas and ELT3 cells. In the normal myometrium, PR-A and PR-B levels varied during the estrous cycle with low ratios of PR-A relative to PR-B (PR-A/PR-B) coinciding with times of cell proliferation. Although PR ligands had no effect on basal levels of uterine leiomyoma cell proliferation in vitro, both progestins and antiprogestins inhibited E(2)-stimulated cell proliferation. In addition, E(2)-stimulated transactivation of an estrogen-response-element reporter gene as well as E(2)-induced upregulation of the PR were also inhibited by PR ligands. These data indicate that PR ligands can transdominantly suppress estrogen receptor signaling and stimulation of uterine leiomyoma cell growth.     

Estrogen stimulation of deoxyribonucleic acid synthesis in uterine epithelial cells which lack estrogen receptors

Autoradiographic studies from this laboratory have previously indicated that the uterine epithelium of the neonatal mouse is devoid of estrogen receptors. The neonatal murine uterus is composed of an undifferentiated mesenchyme and a simple columnar epithelium lining the lumen. In the present study, a method for measuring whole cell uptake of 16 alpha-[125I]iodoestradiol ([125I]iodo-E2) was developed and applied to enzymatically separated, isolated epithelial and mesenchymal cells of neonatal (4-5 days postnatal) uteri. Epithelial cells and fibromuscular cells (stromal and myometrial cells) from uteri of 21-day-old animals were used to validate the assay method. A component of the uptake of [125I]iodo-E2 by cells from 21-day-old uteri was shown to be specific, saturable, and of high affinity. Kd values for specific uptake by uterine mesenchymal and epithelial cells were 1.2-1.3 nM. Maximal specific uptake was 9.3 and 4.2 fmol/micrograms DNA for epithelial and mesenchymal cells, respectively. The uterine epithelial cells of 4- and 5-day-old mice showed no measurable specific uptake of [125I]iodo-E2, while the mesenchymal cells from these animals had a maximal specific uptake of 7.9 fmol/micrograms DNA, with a Kd of 1.3 nM. DNA synthesis increased within the uterine epithelium of neonatal mice after estrogen treatment. The thymidine labeling index was doubled 10 h after a single dose of diethylstilbestrol (DES) and returned to pretreatment values by 18 h. The epithelial mitotic index was also 2-fold higher than control values 16-18 h after DES treatment. The increase in the thymidine labeling index was specific to estrogen treatment. DES did not induce the production of estrogen receptors in neonatal uterine epithelium. Epithelial cells of 5-day-old mice that were treated with DES showed no specific [125I]iodo-E2 uptake, while whole cell uptake by mesenchymal cells from these animals exhibited a specific, high affinity component, with a maximal binding of 8.4 fmol/micrograms DNA. Autoradiographic analysis of [3H]estradiol uptake by uterine tissues from 5-day-old mice 12 h after DES treatment did not show nuclear concentration of the steroid in the epithelial cells. These results indicate that the uterine epithelium of the neonatal mouse is indeed devoid of estrogen receptors, and yet the rate of DNA synthesis within this tissue is responsive to estrogen stimulation. The epithelial cells remain devoid of estrogen receptors after DES stimulation, indicating that intraepithelial estrogen receptors are not required for induction of DNA synthesis in these cells in situ. Possible mechanisms by which this phenomenon may occur are discussed.     

Control of uterine estrogen receptor levels by progesterone.

The mechanism by which progesterone antagonizes estrogenic stimulation of uterine growth was examined in the immature rat. Rats received daily injections of 2.5 mug estradiol (E) for 2 days and on day 3 either 2.5 mug E or 2.5 mug E plus 2.5 mg of progesterone (P). The quantity of nuclear and cytoplasmic estrogen receptor was determined by [3H]estradiol exchange at various intervals after injection of E or E + P. In both groups, nuclear receptor estrogen complex (RnE) increased dramtically one hour after injection and showed a gradual decline from 4 to 24 h after injection. The quantity of cytoplasmic receptor, Rc, decreased to low levels by one hour and began a gradual increase from 4 to 8 h in both groups. However, between 8 and 24 h after injection, the level of Rc continued to increase in the E treatment group (2.39 +/- 0.21 pmol/uterus at 24 h) but remained at the 8 h level in the E + P group (1.09 +/- 0.04 pmol/uterus at 24 h). This observation suggests that two seperate processes are involved in the replenishment of Rc and that progesterone inhibits the second phase of replenishment. The binding affinity and specificity of Rc for estrogens following E + P pretreatment were identical to those of the E pretreatment group. Therefore, P does not alter the binding properties but rather the intrauterine level of Rc. Treatment with E on day 4, when Rc levels differ between E and E + P groups, stimulated uterine weight and protein content on day 5 in the E pretreatment group. However, minimal stimulation was observed in the E + P pretreatment group. The quantity of RnE and the time of nuclear retention of RnE following E injection on day 4 was greater in the E group than in the E + P group. The effect of progesterone on Rc replenishment was dose-dependent (range, 0.1-2.5 mg; 1/2 maximal, 0.5 mg). Injection of testosterone propionate (1.0 mg), a weak estrogen antagonist, with E on day 3 resulted in slightly reduced levels of Rc on day 4. This reduction also correlated with a reduced sensitivity to treatment with E on day 4. These data, together with previous studies from our laboratory, suggest that progesterone and other estrogen antagonists such as nafoxidine and testosterone propionate inhibit estrogen action by interfering with the replenishment of Rc, thereby reducing the number of receptor estrogen complexes that are translocated and retained by uterine nuclei.     

Kinetic alterations in estrogen receptors associated with estrogen receptor processing in human breast cancer cells

After nuclear translocation of estrogen receptors in MCF-7 human breast cancer cells, a processing takes place resulting in a 30-70% decline in the number of estradiol-binding sites measured in nuclear extracts. We have investigated the mechanism of estrogen receptor processing and obtained evidence that multiple events are involved. We confirm, as others have shown previously, that processing involves a decrease in the amount of estradiol binding in MCF-7 cells. In addition, evidence is provided for the generation of a rapidly dissociating population of estradiol-binding sites as an early event in processing. There is a single, slowly dissociating population of estrogen binding sites when MCF-7 cells are exposed to estradiol in the presence of actinomycin D, an inhibitor of receptor processing. One hour after the addition of sufficient estradiol to induce receptor processing, an additional, more rapidly dissociating population of estrogen binding sites is detected. When cells are exposed to estradiol and ethidium bromide, a drug which shares many actions with actinomycin D, but does not inhibit receptor processing, the rapidly dissociating population of estradiol-binding sites is again observed. Significantly, the loss of estradiol-binding sites from MCF-7 cells associated with processing between 1 and 6 h of estradiol exposure, occurs exclusively from the rapidly dissociating population of sites. Whole cell equilibrium-binding assays were performed with MCF-7 cells after 30 min or 5 h of estradiol exposure to determine whether the detected changes in estradiol dissociation reflected affinity changes in a subpopulation of estrogen-binding sites. Although the number of sites detected per cell varied with the assay method employed, binding to a single saturable class of higher affinity sites is always observed. High affinity estradiol-binding sites were reduced by 45% after a 5-h incubation with estradiol in both assay methods. The loss of estradiol binding during processing may therefore be explained by the conversion of certain high affinity estrogen receptors to a rapidly dissociating form which then fails to rebind hormone, or undergoes subsequent reactions that destroy hormone binding activity. Additionally, after 6 h of exposure to estradiol, the remaining receptor-bound estradiol dissociates from intact cells with a rate increased by 50% over that seen from the slow dissociating receptors present at 1 h.(ABSTRACT TRUNCATED AT 400 WORDS)     

Immunofluorescent analysis of estrogen induction of progesterone receptor in the rhesus uterus

Estrogen (E) has been shown to induce an increase in progesterone (P) receptor (PR) concentration in uterine tissue of both rodents and primates. Because of the presence of different cell types within the uterus, we were interested in determining whether estrogen-induced PR were cell type specific in the nonhuman primate uterus (rhesus monkey). Immunofluorescent analyses of E receptor (ER) and PR were performed on fresh frozen cryostat sections (6 microns) of uterine tissue from ovariectomized (3 months) and estradiol (E2)-treated (peak level of E2 during an artificial menstrual cycle) rhesus monkeys. Antibodies to ER and PR were obtained from Abbott Laboratories (H222) and Transbio (MPR1). The avidin-biotin complex technique was used with streptavidin-conjugated Texas red for fluorescent detection. Ovariectomized monkeys showed positive fluorescence for ER in luminal and glandular epithelia, stromal cells, and smooth muscle cells of the myometrium. In contrast, positive fluorescence for PR was observed primarily in glandular epithelia, with little or no fluorescent detection in luminal epithelium, stromal cells, or myometrial smooth muscle cells. After E2 treatment strong positive fluorescence for PR was observed in luminal and glandular epithelia, stromal cells, and myometrial smooth muscle cells. Strong positive fluorescence for ER was also observed in the same cell types. Fluorescent detection of ER and PR was restricted to the nuclei of these cell types. These studies show that ER are present constitutively in all cell types of the E-withdrawn (ovariectomized) nonhuman primate uterus, whereas PR are primarily restricted to glandular epithelia. E2 treatment, which simulated the follicular phase and E2 surge, resulted in the appearance of immunofluorescent PR in luminal epithelia, stromal cells, and myometrial smooth muscle cells. These studies serve to define the cellular pattern of E2-induced PR in the primate uterus.     

Immunocytochemical demonstration of estrogen and progesterone receptors in muscle cells of uterine arteries in rabbits and humans

Modifications of uterine blood flow are implicated in many important aspects of reproductive physiology and in several of their pathological disorders. These modifications are hormonally regulated but remain poorly understood, and various complex mechanisms have been proposed. The aim of this study was to investigate the presence and some characteristics of estrogen receptors (ER) and progesterone receptors (PR) in uterine blood vessels. Using monoclonal antibodies and immunocytochemistry we observed the presence of ER and PR in muscle cells (tunica media) of uterine arteries of rabbits and women. ER or PR immunoreactivity was not detected in the endothelium of uterine arteries nor in uterine capillaries or veins. Staining for both receptors was also present in arterial walls from the fallopian tube (isthmus and ampulla) and vagina but not in arteries of nonreproductive tissues (intestinal, renal, hepatic, femoral, and pulmonary arteries, aorta). PR immuno-staining was increased by estrogen in all cell types of the rabbit uterus, but the doses necessary to provoke an intense nuclear staining in uterine arteries were higher than those required for observing strong labeling in glandular, stromal, or myometrial cells. These results suggest that, contrary to many hypotheses previously put forward, sex steroid hormones may regulate uterine blood flow through a direct effect on uterine arterial walls.     

Immunohistochemical analysis of human uterine estrogen and progesterone receptors throughout the menstrual cycle

Estrogen receptors (ER) and progesterone receptors (PgR) were studied immunohistochemically using specific antireceptor monoclonal antibodies in uterine tissue samples from 33 women in various stages of the menstrual cycle. Immunohistochemical localization was quantified as to intensity of staining and tissue distribution in glandular epithelium, stroma, and myometrium, and the results were compared with those of standard ligand binding assays. In all samples ER and PgR localized within the nuclei of target cells. The maximal concentrations of ER and PgR occurred in the mid- to late proliferative phase of the menstrual cycle. ER content declined throughout the secretory phase. In contrast, PgR content underwent unexpectedly complex and dyssynchronous fluctuations during the secretory phase of the menstrual cycle. Specifically, the glandular epithelium had diminished PgR content, while the stroma and myometrium maintained a significant PgR content. PgR and perhaps ER are not concordant in different cell types within the uterus. Segregation of function through alteration of receptor content may be an important mechanism in steroid-dependent growth and differentiation of target tissues.     

Estrogen and progesterone receptors in the human vagina

Estrogen (E) and progesterone (Pg) receptor (R) levels were determined in the human vagina in relation to menopausal status, day of ovarian cycle and pregnancy. The results obtained confirmed that the human vagina contains ER and, in addition, demonstrated for the first time the presence of PgR in this organ in humans. In cycling women, ER and PgR did not vary significantly during the ovarian cycle; however low (less than or equal to 10 fmoles/mg cytosol protein) concentrations of PgR were more frequently (6 out of 8 cases) detected during the secretory phase. No substantial difference was seen in ER and PgR values between anterior and posterior wall of the vagina. In postmenopausal patients the levels of ER (range: 10-83 fmoles/mg) were similar to those found in premenopause (range: 12-78 fmoles/mg). As regards PgR, the majority (14 out of 20) of vaginae were devoid of PgR, 4 had a very low (less than or equal to 6 fmoles/mg) PgR content and only 2 cases had a PgR level higher than 10 fmol/mg cytosol protein. In pregnant patients (6th to 8th week) ER were found in all vaginae, while PgR were present only in some cases (3 out of 8). It was concluded that the behavior of ER in the human vagina seems different from that in the human endometrium, since ER levels do not vary in relation to changes in the concentrations of sexual hormones in the circulation. On the contrary, PgR levels appear to depend on blood estradiol and progesterone concentration, as in other target tissues.     

Estrogen and progesterone receptors in esophageal carcinoma

SUMMARY.  Information is sparse and contradictory in the literature regarding the role of estrogen receptor (ER) and progesterone receptor (PR) in esophageal carcinoma. This study was conducted over a period of 18 months from September 2004 with the primary aim of determining the PR, ER alpha (ERα) and ER beta (ERβ) status of esophageal carcinoma and normal esophageal mucosa (NEM). The receptor status was correlated with tumor type, tumor differentiation and tumor stage. A total of 45 patients with histologically proven squamous cell carcinoma (SCC) ( n  = 30) and adenocarcinoma (AC) ( n  = 15) were studied. Receptor status was detected by immunohistochemistry (IHC) and semiquantitative assessment was done by quick score method of endoscopic biopsy specimens. The mean age for SCC and AC were not significantly different. The gender ratio in favor of males was 3 : 2 for SCC and 4 : 1 for AC. None of the specimens from SCC or AC showed positivity for PR both in NEM and tumor tissue. Likewise none of the specimens were positive for ERα by IHC. The mean ERβ score for AC was significantly higher than SCC. For SCC it was seen that ERβ positivity in tumor cells increases with dedifferentiation and increasing tumor stage. This trend was seen for AC as well. ERβ is over-expressed in poorly differentiated SCC and AC compared to NEM. Thus ERβ may be a marker for poor biological behavior, that is dedifferentiation or higher stage of disease. In view of these findings we propose a large-scale prospective, longitudinal interventional study using selective estrogen modulators.     

Estrogen and progesterone receptors in human gallbladder

Gallbladder disease is more prevalent in women than men. Estrogen therapy has been associated with an increased incidence of gallbladder disease in both sexes. Further, increased progesterone levels have been implicated in impairment of gallbladder motility in pregnancy. Because sex hormones often exert their action through specific receptors, we investigated whether human gallbladder contains receptors for estrogen and progesterone. Binding of radiolabeled hormones in cytosol and nuclei prepared from human gallbladder of both sexes is indicative of the presence of receptors for both estrogen and progesterone. The binding is saturable, of high affinity and highly specific for its particular type of hormone but not other steroids. Fractionation of sodium molybdate-stabilized gallbladder cytosol on Sephadex G-100 demonstrates that the labeled hormones are not bound to defined proteins such as sex steroid binding globulin or albumin. These studies indicate that human gallbladder contains both estrogen and progesterone receptors, that the presence of these receptors may explain the sensitivity of gallbladder tissue to these hormones and that certain aspects of gallbladder function may be mediated by the interaction of steroid hormones with these receptors.     

Effect of estrogen agonists and antagonists on induction of progesterone receptor in a rat hypothalamic cell line.

Estrogen is essential in the hypothalamus for the central regulation of reproduction. To understand the molecular mechanism(s) of estrogen action in the hypothalamus, immortalized rat embryonic hypothalamic cell lines were characterized for steroid receptors and subcloned. Scatchard analysis of the D12 subclone demonstrated one high affinity estrogen receptor-binding site (Kd = 31.3+/-1.9 pM) with a Bmax of 30.8+/-0.8 fmol/mg. Estrogen receptor-alpha protein was identified by Western blot and gel shift analyses. Treatment with estradiol (48 h) stimulated progesterone receptor (PR) messenger RNA expression and binding to [3H]R5020, a synthetic progestin. Because the agonist or antagonist activity of estrogen mimetics can be cell type dependent, the activities of various estrogen mimetics were determined in D12 cells. ICI 182,780 (IC50 = 0.63 nM), raloxifene (IC50 = 1 nM), enclomiphene (IC50 = 77 nM), and tamoxifen (IC50 = 174 nM) inhibited the induction of PR by estradiol, and none of these compounds significantly stimulated PR when given alone. In contrast, 17alpha-ethynyl estradiol (EC50 = 0.014 nM), zuclomiphene (EC50 = 100 nM), and genistein (EC50 = 17.5 nM) functioned as estrogen agonists in these cells. In addition, the estrogen-induced progesterone receptor activated a progesterone response element reporter construct in response to progestins. Thus, the D12 rat hypothalamic cell line provides a useful model for characterizing tissue-selective estrogenic compounds, identifying estrogen- and progesterone-regulated hypothalamic genes, and understanding the molecular mechanisms of steroid action in various physiological processes mediated by the hypothalamus.     

Correlation between in vitro growth and regulation of estrogen and progesterone receptors in rat mammary epithelial cells

The present studies examine 1) the effect of enzymatic cell dissociation on the level of cytosolic estrogen receptor (ER) and progesterone receptor (PR) for normal rat mammary tissue, 2) the concentrations of ER and PR in rat mammary epithelial (RME) cells cultured within collagen gel, and 3) correlations that may exist between receptor concentration and cultured RME cell proliferation after hormonal stimulation in vitro. After cell dissociation, ER was present in mammary cells at higher concentrations than those found in the whole gland, whereas PR concentrations were similar to those in the whole gland. As characterized by Scatchard analysis, PR and, to a lesser extent, ER can be maintained in cells cultured in serum-free medium within a collagen gel matrix. ER is apparently functional at relatively low levels, since estradiol did induce PR synthesis, and cytosolic ER was reduced by estrogen administration. However, estradiol had no mitogenic effect on RME cells in this system, supporting the hypothesis that there may be a dichotomy between estrogen's effect on growth and progesterone receptor synthesis. PRL plus progesterone act synergistically to induce cell proliferation in our system, and this correlates with increased concentrations of progesterone receptors. Thus, the collagen gel system appears to provide a useful in vitro model for the study of receptor regulation and cell proliferation.     

Differential regulation of proteasome-dependent estrogen receptor alpha and beta turnover in cultured human uterine artery endothelial cells

Estrogen-induced loss of estrogen receptor (ER) alpha expression limits estrogen responsiveness in many target cells. However, whether such a mechanism contributes to changes in vascular endothelial ER alpha and/or ER beta levels is unclear. Using RT-PCR assays, we did not find any regulation of ER alpha or ER beta mRNA expression in human uterine artery endothelial cell (HUAEC) nuclear extracts on stimulation with 17 beta-estradiol for 1 or 2 h. By contrast, Western analysis on HUAEC extracts revealed that 17 beta-estradiol was capable of down-regulating both ER alpha and ER beta protein starting 1 h after treatment, an effect that can be blocked by pretreatment with tamoxifen as well as with the proteasome inhibitor lactacystin. The proteolysis inhibitors insulin, cycloheximide, and puromycin impede ER alpha, but not ER beta, turnover. Ubiquitin, but not its competitive inhibitor methyl-ubiquitin, induces rapid turnover of both ERs in a cell-free system of MCF-7 and HUAEC extracts. We, thus, propose the existence of estrogen-induced ER degradation that serves to control physiological responses in an estrogen target tissue, i.e. human vascular endothelium, by down- regulating ER alpha as well as ER beta through different proteasomal uptake mechanisms.     

Differential uterine expression of estrogen and progesterone receptors correlates with uterine preparation for implantation and decidualization in the mouse.

The present investigation examined the spatiotemporal expression of estrogen receptors (ER-alpha and ER-beta) and progesterone receptor (PR) in the periimplantation mouse uterus (days 1-8). ER-alpha messenger RNA (mRNA) was detected at much higher levels in the periimplantation uterus compared with that of ER-beta mRNA, the levels of which were very low in all uterine cells during this period. Results of in situ hybridization demonstrated expression of ER-alpha mRNA primarily in the luminal and glandular epithelia on days 1 and 2 of pregnancy. On days 3 and 4, the accumulation was localized primarily in stromal cells in addition to its presence in the epithelium. Following implantation on day 5, the accumulation of this mRNA was more condensed in the luminal and glandular epithelia, but declined in the subluminal epithelial stroma at the sites of implanting embryos. On days 6-8, the accumulation of ER-alpha mRNA was primarily localized in the secondary decidual zone (SDZ) with more intense localization in the subepithelial cells at the mesometrial pole. In contrast, signals were very low to undetectable in the primary decidual zone (PDZ), and no signals were detected in implanting embryos. The undifferentiated stroma underneath the myometrium also showed positive signals. The immunolocalization of ER-alpha protein correlated with the mRNA localization. Western blot analysis showed down-regulation of ER-alpha in day 8 decidual cell extracts consistent with the down-regulation of ER-alpha mRNA in decidual cells immediately surrounding the embryo on this day. The expression pattern of PR was also dynamic in the periimplantation uterus. On day 1, the accumulation of PR mRNA was very low to undetectable, whereas only a modest level of accumulation in the epithelium was noted on day 2. On days 3 and 4, the accumulation of this mRNA was detected in both the epithelium and stroma. In contrast, the expression was restricted only to the stroma with increased signals at the sites of implantation on day 5. On days 6-8, PR mRNA accumulation increased dramatically throughout the deciduum. The localization of immunoreactive PR correlated with the mRNA distribution in the periimplantation uterus. Taken together, the results demonstrate that the expression of ER-alpha, ER-beta, and PR is differentially regulated in the periimplantation mouse uterus. This compartmentalized expression of ER and PR provides information regarding the sites of coordinated effects ofestrogen and progesterone in the preparation of the uterus for implantation and decidualization during early pregnancy.     

Sugar and amino acid transport from the rat uterine lumen: effects of estrogen and progesterone

Sugar and amino acid transport and diffusion from the uterine lumen were evaluated in either castrated rats 4 or 24 h after iv injection of 17 beta-estradiol (0.1--10 microgram) or in estrogen-primed castrated rats 12 or 24 h after iv injection of progesterone (25--250 microgram). Uptake phenomena were evaluated by selectively exposing the uterine luminal surface to a Ringer's solution containing [U-14C]D-mannitol and [3H]3-O-methyl-D-glucose or [3H]alpha-aminoisobutyric acid for a 30-sec incubation. Diffusion (D-mannitol uptake) decreased significantly 4 h (but not 24 h) after estrogen and 12 and 24 h after progesterone treatment. [3H]3-O-methyl-D-glucose transport increased significantly both 4 h (120--380%) and 24 h (50--200%) after estrogen. Although [3H]3-O-methyl-D-glucose transport was not significantly changed from that in the vehicle-injected control 12 or 24 h after progesterone, comparison of the transport at 12 h (reduced) to that at 24 h (increased) revealed a significant difference in the responses to progesterone treatment at these two times. [3H]alpha-aminoisobutyric acid transport increased significantly 4 and 24 h after only a pharmacological dose of 17 beta-estradiol and was unchanged 24 h after progesterone administration. In summary, uterine luminal diffusion and transport phenomena are hormone sensitive, with estrogen exerting a more pronounced effect on transport than does progesterone. Thus, through modulation of luminal transport mechanisms, these hormones may regulate substrate levels and, hence, their availability to the developing conceptus during different reproductive states in the rat.