Regulation of progesterone receptors and decidualization in uterine stroma of the estrogen receptor-alpha knockout mouse

Regulation of progesterone receptor (PR) in uterine stroma (endometrial stroma plus myometrium) by estrogen was investigated in estrogen receptor-alpha (ERalpha) knockout (alphaERKO) mice. 17 beta-Estradiol (E(2)) increased PR levels in uterine stroma of ovariectomized alphaERKO mice, and ICI 182 780 (ICI) inhibited this E(2)-induced PR expression. Estrogen receptor-beta(ER beta) was detected in both uterine epithelium and stroma of wild-type and alphaERKO mice by immunohistochemistry. In organ cultures of alphaERKO uterus, both E(2) and diethylstilbestrol induced stromal PR, and ICI inhibited this induction. These findings suggest that estrogen induces stromal PR via ERbeta in alphaERKO uterus. However, this process is not mediated exclusively by ERbeta+, because in ERbeta knockout mice, which express ERalpha, PR was up-regulated by E(2) in uterine stroma. In both wild-type and alphaERKO mice, progesterone and mechanical traumatization were essential and sufficient to induce decidual cells, even though E(2) and ERalpha were also required for increase in uterine weight. Progesterone receptor was strongly expressed in decidual cells in alphaERKO mice, and ICI did not inhibit decidualization or PR expression. This study suggests that up-regulation of PR in endometrial stroma is mediated through at least three mechanisms: 1) classical estrogen signaling through ERalpha, 2) estrogen signaling through ERbeta, and 3) as a result of mechanical stimulation plus progesterone, which induces stromal cells to differentiate into decidual cells. Each of these pathways can function independently of the others.     

A comparative study of estrogen receptors alpha and beta in the rat uterus.

The uterus is an important target organ for steroid hormones. The effects of these hormones are mediated via specific receptors. The aim of this study was to compare the expression, distribution, and regulation of estrogen receptor (ER) alpha and beta in the rat uterus in order to establish possible different biological roles for the two receptor forms. Ovariectomized rats were treated with either estradiol (E(2)), progesterone (P(4)), or combinations of these for 24 or 48 h. The mRNA levels were measured by solution hybridization. Distribution of the mRNAs and receptor proteins was detected by in situ hybridization and immunohistochemistry. The results showed that ERalpha is the dominating subtype in the rat uterus. E(2) seemed to increase the ERalpha mRNA level in the glandular and luminal epithelium, but it caused a decrease of the immunostaining intensity in the glandular epithelium. P(4) reduced ERalpha expression in luminal epithelium whereas no effect was seen in the glandular epithelium. E(2) or P(4) did not alter the expression of ERbeta, on either the mRNA or protein level. In conclusion, the distribution and regulation of ERalpha and ERbeta differ in the different compartments of the rat uterus. The complex uterine responses to E(2) and P(4) are directly or indirectly mediated by differential cell-specific expression of their receptors. The low expression in the uterus and the limited regulation by gonadal steroids in this study suggest that ERbeta probably plays a minor role in the regulation of uterine physiology.     

Involvement of androgen receptor in 17beta-estradiol-induced cell proliferation in rat uterus

Although it is known that, in the uterus, estrogen receptor alpha (ERalpha) is involved in proliferation and progesterone receptor in differentiation, the role of the two other gonadal-hormone receptors expressed in the uterus, androgen receptor (AR) and estrogen receptor beta (ERbeta), remains undefined. In this study, the involvement of AR in 17beta-estradiol (E(2))-induced cellular proliferation in the immature rat uterus was investigated. AR levels were low in the untreated immature uterus, but 24 h after treatment of rats with E(2), there was an increase in the levels of AR and of two androgen-regulated genes, IGF-I and Crisp (cysteine-rich secretory protein). As expected, E(2) induced proliferation of luminal epithelial cells. These actions of E(2) were all blocked by both the antiestrogen tamoxifen and the antiandrogen flutamide. The E(2)-induced AR was found by immunohistochemistry to be localized exclusively in the stroma, mainly in the myometrium, where it colocalized with ERalpha but not with ERbeta. ERbeta, detected with two different ERbeta-specific antibodies, was expressed in both stromal and epithelial cells either alone or together with ERalpha. Treatment with E(2) caused down-regulation of ERalpha and ERbeta in the epithelium. The data suggest that, in E(2)-induced epithelial cell proliferation, ERalpha induces stromal AR and AR amplifies the ERalpha signal by induction of IGF-I. Because AR is never expressed in cells with ERbeta, it is unlikely that ERbeta signaling is involved in this pathway. These results indicate an important role for AR in proliferation of the uterus, where estrogen and androgen do not represent separate pathways but are sequential steps in one pathway.     

Messenger RNA levels of estrogen receptors alpha and beta and progesterone receptors in the cyclic and inseminated/early pregnant sow uterus

The aim of the present study was to investigate differences in the expression of mRNAs for ERalpha, ERbeta and PR in the sow uterus at different stages of the estrous cycle as well as in inseminated sows at estrus and during early pregnancy by use of solution hybridization and in relation to plasma levels of estradiol and progesterone. Uterine samples were collected at different stages of the estrous cycle and after insemination/early pregnancy. In the endometrium, the expression of ERalpha mRNA and PR mRNA was similar for cyclic and early pregnant groups. Both were highest at early diestrus/70 h after ovulation and ERalpha mRNA was lowest at late diestrus/d 19 while PR mRNA was lowest at diestrus and late diestrus/d 11 and d 19. The expression of endometrial ERbeta was constantly low during the estrous cycle but higher expression was found in inseminated/early pregnant sows at estrus and 70 h after ovulation. In the myometrium, high expression of ERalpha mRNA and PR mRNA was observed at proestrus and estrus in cyclic sows and at estrus in newly inseminated sows. Higher expression of myometrial ERbeta mRNA was found in inseminated/early pregnant sows compared with cyclic sows, although significant only at estrus. In conclusion, the expression of mRNAs for ERalpha, ERbeta and PR in the sow uterus differed between endometrium and myometrium as well as with stages of the estrous cycle and early pregnancy. In addition to plasma steroid levels, the differences between cyclic and inseminated/early pregnant sows suggest that other factors, e.g. insemination and/or the presence of embryos, influence the expression of these steroid receptor mRNAs in the sow uterus.     

Effect of sex hormones on renal estrogen and angiotensin type 1 receptors in female and male rats

Although the mechanisms are not understood, evidence suggests that 17beta-estradiol (E2) confers protection from cardiovascular and renal complications in many diseases. We have reported that E2 decreases angiotensin type 1 receptors (AT1Rs) in different tissues and hypothesize that E2 exerts tonic inhibition on AT1Rs, reducing effects of ANG II. This study determined the effects of E2 and dihydrotestosterone (DHT) on cortical estrogen receptors (ERs) and glomerular AT1R binding in rats. Animals underwent sham operation, ovariectomy (Ovx) or orchidectomy (Cas) and were treated (Ovx +/- E2; Cas +/- DHT) for 3 wk. Cortical ERalpha protein was 2.5 times greater, and ERbeta was 80% less in females vs. males (P < 0.01). Glomerular AT1R binding was lower in females than males [4,657 +/- 838 vs. 7,457 +/- 467 counts per minute (cpm), P < 0.01]. Ovx reduced ERalpha protein by 50%, whereas E2 increased ERalpha expression after Ovx. The decrease in cortical ERalpha in Ovx rats was associated with a significant increase in AT1R binding (6,908 +/- 609 cpm), and E2 prevented this increase. There was no change in ERalpha or AT1R binding following Cas +/- DHT (25 mg) treatment, although Cas did elevate cortical ERbeta (P < 0.01). Interestingly, the high dose DHT (200 mg) elevated ERalpha 150% above intact levels and profoundly decreased AT1R binding (1,824 +/- 705 cpm, P < 0.001 vs. intact male). This indicates that under normal conditions, glomerular AT1R binding is significantly greater in male than female animals, which may be important in development of cardiovascular and renal disease in males. Furthermore, E2 regulates ERalpha and is inversely associated with glomerular AT1R binding, supporting our hypothesis that E2 tonically suppresses AT1Rs and suggesting a potential mechanism for the protective effects of estrogen.     

Estrogen and antiestrogen effects on neonatal ovine uterine development

Postnatal development of the ovine uterus between birth and Postnatal Day (PND) 56 involves differentiation of the endometrial glandular epithelium from the luminal epithelium followed by tubulogenesis and branching morphogenesis. These critical events coincide with expression of estrogen receptor alpha (ERalpha) by nascent endometrial glands and stroma. To test the working hypothesis that estrogen and uterine ERalpha regulate uterine growth and endometrial gland morphogenesis in the neonatal ewe, ewes were treated daily from birth (PND 0) to PND 55 with 1) saline and corn oil as a vehicle control (CX), 2) estradiol-17 beta (E2) valerate (EV), an ERalpha agonist, 3) EM-800, an ERalpha antagonist, or 4) CGS 20267, a nonsteroidal aromatase inhibitor. On PND 14, ewes were hemihysterectomized, and the ipsilateral oviduct and ovary were removed. The remaining uterine horn, oviduct, and ovary were removed on PND 56. Treatment with CGS 20267 decreased plasma E2 levels, whereas EM-800 had no effect compared with CX ewes. Uterine horn weight and length were not affected by EM-800 or CGS 20267 but were decreased in EV ewes on PND 56. On PND 14 and PND 56, treatment with EV decreased endometrial thickness but increased myometrial thickness. The numbers of ductal gland invaginations and endometrial glands were not affected by CGS but were lower in EM-800 ewes on PND 56. Exposure to EV completely inhibited endometrial gland development and induced luminal epithelial hypertrophy but did not alter uterine cell proliferation. Exposure to EV substantially decreased expression of ERalpha, insulin-like growth factor (IGF) I, and IGF-II in the endometrium. Results indicate that circulating E2 does not regulate endometrial gland differentiation or development. Although ERalpha does not regulate initial differentiation of the endometrial glandular epithelium, results indicate that ERalpha does regulate, in part, coiling and branching morphogenesis of endometrial glands in the neonatal ewe. Ablation of endometrial gland genesis by EV indicates that postnatal uterine development is extremely sensitive to the detrimental effects of inappropriate steroid exposure.     

Quantitative analysis of estrogen receptor proteins in rat ovary

The mRNAs of estrogen receptor beta (ERbeta), and its splice variant, ERbeta2, are abundant in granulosa cells in the ovary. With the use of antibodies, ERbeta protein has also been shown to be abundantly expressed, but to date no ERbeta2 protein has been demonstrated in the ovary. ERbeta2 has a peptide, 18 amino acids in length, inserted into its ligand-binding domain, resulting in a reported 35-fold reduction in its affinity for estrogen (E2). ERalpha, ERbeta1 and ERbeta2 were quantified by Western blotting and by RT-PCR and their cellular localization in the ovary was examined by immunohistochemistry. In 3- and 5-week-old virgin, pregnant, lactating and post-lactating rats, the level of ERalpha protein ranged between 1.6 and 3.8 fmol/microg total protein. That of ERbeta was 8.8-11.2 and of ERbeta2, in the same samples, 4.1-5.9 fmol/microg total protein. ERbeta2 and ERbeta1 proteins were, therefore, present in approximately equal amounts in the ovary throughout the various reproductive stages. The major ERbeta proteins in rat ovary, detected by their molecular weights on Western blots, were ERbeta1-530 and ERbeta2-548 (530+18 amino acids (aa)). Immunohistochemical staining revealed that ERbeta and ERbeta2 were expressed predominantly in granulosa cells of growing follicles, while ERalpha was found only in theca cells. In some theca cells, both ERalpha, ERbeta2 were expressed. The data suggests that in theca cells, where it is co expressed with ERalpha, ERbeta2 could function as a repressor of ERalpha. However, in granulosa cells where no ERalpha is detectable, and where E2 levels are high, ERbeta2, with its low affinity for E2, could be an important sensor through which E2 exerts regulatory control.     

Toxic effects of in vitro exposure to p-tert-octylphenol on bovine oocyte maturation and developmental competence

Alkylphenolic compounds are a widespread family of xenoestrogens. High concentrations of these substances are present in sewage sludge that is spread on arable land and pasture as fertilizer. Because of their known endocrine system-disrupting activity, alkylphenols represent a potential risk for the reproductive health of farm animals. In this study, the impact of p-tert-octylphenol (OP) on the developmental competence of bovine oocytes was evaluated. Endocrine activity of OP was investigated for its effect on estrogen receptors alpha and beta (ERalpha and ERbeta) and progesterone receptor (PR) mRNA levels. Cumulus-oocyte complexes (COCs) were exposed during in vitro maturation to serial concentrations of OP (1-0.0001 microg/ml) and were compared with vehicle-treated controls and a group of COCs treated with 17 beta-estradiol (E2). A dose-related decrease in the percentage of oocytes that completed maturation after 24 h and in oocyte fertilization competence was observed at doses of OP as low as 0.01 microg/ml. Groups treated with > or =0.001 microg/ml OP showed impaired embryo development. No adverse effects of E2 were observed. In the E2-treated COCs, ERalpha mRNA was decreased but PR mRNA was upregulated compared with controls. Treatment with 0.001 and 0.0001 microg/ml OP induced a decrease in ERalpha mRNA, but ERbeta and PR mRNA were not affected. Treatment with 0.01 microg/ml OP did not produce changes in the expression of any of the mRNAs studied. OP impairs meiotic progression and developmental competence of bovine oocytes without demonstrating clear estrogen-mimic activity.     

The aryl hydrocarbon receptor mediates degradation of estrogen receptor alpha through activation of proteasomes

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other aryl hydrocarbon receptor (AhR) ligands suppress 17beta-estradiol (E)-induced responses in the rodent uterus and mammary tumors and in human breast cancer cells. Treatment of ZR-75, T47D, and MCF-7 human breast cancer cells with TCDD induces proteasome-dependent degradation of endogenous estrogen receptor alpha (ERalpha). The proteasome inhibitors MG132, PSI, and PSII inhibit the proteasome-dependent effects induced by TCDD, whereas the protease inhibitors EST, calpain inhibitor II, and chloroquine do not affect this response. ERalpha levels in the mouse uterus and breast cancer cells were significantly lower after cotreatment with E plus TCDD than after treatment with E or TCDD alone, and our results indicate that AhR-mediated inhibition of E-induced transactivation is mainly due to limiting levels of ERalpha in cells cotreated with E plus TCDD. TCDD alone or in combination with E increases formation of ubiquitinated forms of ERalpha, and both coimmunoprecipitation and mammalian two-hybrid assays demonstrate that TCDD induces interaction of the AhR with ERalpha in the presence or absence of E. In contrast, E does not induce AhR-ERalpha interactions. Thus, inhibitory AhR-ERalpha cross talk is linked to a novel pathway for degradation of ERalpha in which TCDD initially induces formation of a nuclear AhR complex which coordinately recruits ERalpha and the proteasome complex, resulting in degradation of both receptors.     

The effects of the selective estrogen receptor modulators, methyl-piperidino-pyrazole (MPP), and raloxifene in normal and cancerous endometrial cell lines and in the murine uterus

Since estrogens have vital functions in the uterus but might also contribute to endometrial cancer, we sought to determine the in vitro effects of methyl-piperidino-pyrazole (MPP), raloxifene, and beta-estradiol on Ishikawa and RL-95 endometrial cancer, and ovine luminal endometrial (oLE) cell lines and the in vivo effects of these compounds in the rodent uterus. MPP and raloxifene (1 nM) induced significant apoptosis in the endometrial cancer and oLE cell lines compared to beta-estradiol treated and control cells (P 相似文献   

Expression of estrogen receptors alpha and beta in the baboon fetal ovary

In adult mammals, estrogen regulates ovarian function, and estrogen receptor (ER) is expressed in granulosa cells of antral follicles of the adult baboon ovary. Because the foundation of adult ovarian function is established in utero, the present study determined whether ERalpha and/or ERbeta were expressed in fetal ovaries obtained on Days 100 (n = 3) and 165-181 (n = 5) of baboon gestation (term = Day 184). On Day 100, ERalpha protein was detected by immunocytochemistry in surface epithelium and mesenchymal-epithelial cells but not oocytes in germ cell cords. ERbeta protein was also detected by immunocytochemistry on Day 100 of gestation and was abundantly expressed in mesenchymal-epithelial cells in germ cell cords, lightly expressed in the germ cells, but was not detected in the surface epithelium. On Days 165-180 of gestation, ERalpha expression was still intense in the surface epithelium, in mesenchymal-epithelial cells throughout the cortex, and in nests of cells between follicles. ERalpha expression was lighter in granulosa cells and was not observed in all granulosa cells, particularly in follicles close to the cortex. In contrast, ERbeta expression was most intense in granulosa cells, especially in flattened granulosa cells, was weaker in mesenchymal-epithelial cells and nests of cells between follicles, and was absent in the surface epithelium. Using an antibody to the carboxy terminal of human ERbeta, ERbeta protein was also detected by Western immunoblot with molecular sizes of 55 and 63 kDa on Day 100 and primarily 55 kDa on Day 180. The mRNAs for ERalpha and ERbeta were also detected by Northern blot analysis in the baboon fetal ovary. These results are the first to establish that the ERalpha and ERbeta mRNAs and proteins are expressed and exhibit changes in localization in the primate fetal ovary between mid and late gestation. Because placental estrogen production and secretion into the baboon fetus increases markedly during advancing pregnancy, we propose that estrogen plays an integral role in programming fetal ovarian development in the primate.     

An immunohistochemical study on the regulation of estrogen receptor alpha by estradiol in the endometrium of the immature ewe

The effects of estradiol-17beta (E2) on the expression of estrogen receptor alpha (ERalpha) in stromal and epithelial cells of endometrium in prepubertal lambs were investigated. Twenty three-month-old lambs were treated or not treated with one, two or three i.m. injections of E2 (1 microg x kg(-1)) in corn oil at intervals of 24 h. Lambs were slaughtered 12 or 24 h after the last injection. An immunohistochemical technique was used to visualize ERalpha immunostaining which was then analyzed quantitatively by a computer imaging analysis system. Seven endometrial compartments defined by cell type and location were analyzed separately. Positive staining of ERalpha was seen in the nuclei of stromal and epithelial cells. Glandular epithelium located next to the myometrium was stained more intensely than that next to the luminal epithelium and this phenomenon was maintained during treatment. Significantly less immunostaining was found in stromal cells 12 and 24 h after the first injection compared to the control group. A similar pattern was found in the glandular epithelium, although the decrease was more pronounced and the restoration of ERalpha was faster. This study shows that E2 treatment down regulates ERalpha in the endometrium temporarily in both stromal and epithelial cells, but the characteristics of this effect seems to be cell type specific.     

Neonatal exposure to endocrine active compounds or an ERbeta agonist increases adult anxiety and aggression in gonadally intact male rats

Endocrine active compounds (EACs) have been shown to influence a number of reproductive endpoints but less is known about how they might affect other hormone dependent behaviors including anxiety and aggression. Recent evidence suggests that these effects may be mediated through the beta form of the estrogen receptor (ERbeta). Using male Long Evans rats, we sought to determine how neonatal exposure to EACs affects anxiety and aggression in adulthood. Anxiety was assessed using the elevated plus maze and aggression was assessed 8 weeks later using the resident intruder test. To gain insight into which ER subtype (ERalpha vs ERbeta) might be mediating these effects we used agonists specific for ERalpha (1,3,5-tris(4-Hydroxyphenyl)-4-propyl-1H-pyrazole (PPT)) or ERbeta (Diarylpropionitrile (DPN)) as additional treatment groups. For these experiments the synthetic EAC bisphenol-A (BPA) and the phytoestrogen metabolite equol (EQ) were used. Male neonates were injected with either 0.05 ml sesame oil (control), 50 microg estradiol benzoate (EB), 1 mg/kg DPN, 1 mg/kg PPT, 50 microg/kg BPA, or 10 mg/kg EQ daily for 4 days beginning on the day of birth (PND 0). Compared to the oil treated controls, significantly fewer open arm entries were made by the males neonatally treated with DPN, EQ, or BPA. The DPN and EQ treated males were also more aggressive compared to the controls. These findings suggest that neonatal exposure to EACs with agonistic activity on ERbeta may influence affective behavior in adulthood, including anxiety and aggression.     

Estrogen receptor-alpha knockout mice exhibit resistance to the developmental effects of neonatal diethylstilbestrol exposure on the female reproductive tract.

Data indicate that estrogen-dependent and -independent pathways are involved in the teratogenic/carcinogenic syndrome that follows developmental exposure to 17beta-estradiol or diethylstilbestrol (DES), a synthetic estrogen. However, the exact role and extent to which each pathway contributes to the resulting pathology remain unknown. We employed the alphaERKO mouse, which lacks estrogen receptor-alpha (ERalpha), to discern the role of ERalpha and estrogen signaling in mediating the effects of neonatal DES exposure. The alphaERKO provides the potential to expose DES actions mediated by the second known ER, ERbeta, and those that are ER-independent. Wild-type and alphaERKO females were treated with vehicle or DES (2 microg/pup/day for Days 1-5) and terminated after 5 days and 2, 4, 8, 12, and 20 months for biochemical and histomorphological analyses. Assays for uterine expression of the genes Hoxa10, Hoxa11, and Wnt7a shortly after treatment indicated significant decreases in DES-treated wild-type but no effect in the alphaERKO. In contrast, the DES effect on uterine expression of Wnt4 and Wnt5a was preserved in both genotypes, suggesting a developmental role for ERbeta. Adult alphaERKO mice exhibited complete resistance to the chronic effects of neonatal DES exposure exhibited in treated wild-type animals, including atrophy, decreased weight, smooth muscle disorganization, and epithelial squamous metaplasia in the uterus; proliferative lesions of the oviduct; and persistent vaginal cornification. Therefore, the lack of DES effects on gene expression and tissue differentiation in the alphaERKO provides unequivocal evidence of an obligatory role for ERalpha in mediating the detrimental actions of neonatal DES exposure in the murine reproductive tract.     

Endometrial surface and secretory alterations associated with embryonic mortality in gilts administered estradiol valerate on days 9 and 10 of gestation

Administration of estrogen to gilts on Days 9 and 10 of pregnancy results in total embryonic loss by Day 18. The present study examined changes in the uterine endometrial surface and secretion during conceptus attachment in control and estrogen-treated (Days 9 and 10) pregnant gilts. Gilts were unilaterally hysterectomized on either Days 12 and 14 or Days 16 and 18 of gestation. Uterine horns were flushed with saline and conceptuses were evaluated. Intact conceptuses were recovered from all control gilts, whereas estrogen-treated gilts contained normal intact conceptuses only on Day 12 of gestation. Antiviral activity, which reflects conceptus viability, was reduced (p less than 0.01) in uterine flushings after Day 14 in estrogen-treated gilts. Culture of endometrial explants with [3H]glucosamine revealed several glycoproteins that are synthesized during the period of conceptus attachment; however, no difference in glycoprotein synthesis between treatment groups was detected by analysis with two-dimensional PAGE and fluorography. Analyses of the uterine epithelium by scanning and transmission electron microscopy demonstrated that estrogen administration caused an alteration in the uterine surface, a thinning of the uterine epithelial glycocalyx, and a reduction of cationic ferritin binding to the microvilli of the uterine epithelium. Results indicate that conceptus mortality after early administration of estrogen is associated with alterations in the uterine endometrial surface during the period of conceptus attachment in the pig.     

Evidence that epithelial and mesenchymal estrogen receptor-alpha mediates effects of estrogen on prostatic epithelium

In combination with androgens, estrogens can induce aberrant growth and malignancy of the prostate gland. Estrogen action is mediated through two receptor subtypes: estrogen receptors alpha (ERalpha) and beta (ERbeta). Wild-type (wt) and transgenic mice lacking a functional ERalpha (alphaERKO) or ERbeta (betaERKO) were treated with the synthetic estrogen diethylstilbestrol (DES). DES induced prostatic squamous metaplasia (SQM) in wt and betaERKO but not in alphaERKO mice, indicating an essential role for ERalpha, but not ERbeta, in the induction of SQM of prostatic epithelium. In order to determine the respective roles of epithelial and stromal ERalpha in this response, the following tissue recombinants were constructed with prostatic epithelia (E) and stroma (S) from wt and ERKO mice: wt-S+wt-E, alphaERKO-S+alphaERKO-E, wt-S+alphaERKO-E, and alphaERKO-S+wt-E. A metaplastic response to DES was observed in wt-S+wt-E tissue recombinants. This response to DES involved multilayering of basal epithelial cells, expression of cytokeratin 10, and up-regulation of the progesterone receptor. Tissue recombinants containing alphaERKO-E and/or -S (alphaERKO-S+alphaERKO-E, wt-S+alphaERKO-E, and alphaERKO-S+wt-E) failed to respond to DES. Therefore, full and uniform epithelial SQM requires ERalpha in the epithelium and stroma. These results provide a novel insight into the cell-cell interactions mediating estrogen action in the prostate via ERalpha.     

Intrauterine migration of the porcine embryo: influence of estradiol-17 beta and histamine

The role of estradiol-17 beta (E2) in migration of the porcine embryo was examined (Experiment 1) by observing the distribution of Silastic (polydimethyl siloxane, Medical Adhesive Silicone Type A, Dow Corning) beads impregnated with cholesterol or E2 (n=5 gilts per treatment) after 5 days in utero (Day 12 of the estrous cycle, Day 0=1st day of estrus). Beads impregnated with E2 migrated farther (P less than 0.05) than those impregnated with cholesterol. Twenty additional gilts and sows were used to determine if histamine was involved with intrauterine migration (Experiment 2). On Day 6 of gestation the tip of each uterine horn was exposed and the subserosa of each of 5 gilts was injected with either vehicle, 8 mg of cromolyn sodium (an inhibitor of histamine release) or 8 mg of cromolyn sodium plus 1 mg of histamine. Four days later (Day 10), the excised uterus was examined for migration of embryos. An additional group of 5 gilts received 8 mg of cromolyn sodium on Days 6 and 10 and were examined on Day 12. Results from the second experiment demonstrated that cromolyn sodium treatment alone restricted (P less than 0.05) Day 10 embryos to the tip of the uterine horn but by Day 12 embryos had overcome this restriction. Injection of histamine overcame the inhibitory effects of cromolyn sodium and restored migration of Day 10 embryos. These experiments suggest that both E2 and histamine are involved in intrauterine migration of the porcine embryo. The extent to which these hormones might be interrelated during migration is not fully understood at this time.     

Silymarin is a selective estrogen receptor beta (ERbeta) agonist and has estrogenic effects in the metaphysis of the femur but no or antiestrogenic effects in the uterus of ovariectomized (ovx) rats

Silymarin is a widely used standardized mixture of flavonolignans and its major component Silybinin binds to cytosolic estrogen receptors. Here, we demonstrate that this binding is exclusive to the estrogen receptor beta (ERbeta). Treatment of ovariectomized (ovx) rats with silymarin or estradiol (E2) may allow differentiation of biological effects mediated by the ERalpha or ERbeta. E2 inhibited serum LH, cholesterol, LDL and HDL concentrations in the blood and increased gene expression of IGF1, HbEGF and C3 in the uterus, while silymarin was totally ineffective or antagonistic in altering these parameters. Both, E2 and silymarin inhibited expression of uterine ERbeta gene. Hence, in the pituitary, liver (where the lipoproteins are synthesized) and uterus E2 acts primarily via the ERalpha. Exclusive estrogenic effects of silymarin were observed in the metaphysis of the femur (MF), on osteoblast parameters (gene expression of IGF1, TGFbeta1, osteoprotegerin, collagen-1alpha1, osteocalcin (OC)) and on the osteoclast activity marker tartrate resistant acid phosphatase (TRAP) gene expression of adult ovx rats. Our RT-PCR method detects ERbeta gene expression in all organs including developing bones but not in the MF of adult ovx rats. We conclude therefore, that the effects of silymarin in this part of the bone cannot be exerted via the ERalpha because it does not bind to this receptor subtype. Despite the failure to detect ERbeta mRNA in the MF of our animals the possibility exists that ERbeta protein is present and may mediate the effects of silymarin. Another possibility may be that the effect of silymarin and therefore possibly also of E2 in the MF may be mediated via other possibly not yet identified receptors or via an ERbeta splice variant which is not detected by our PCR-method.