Endocrine. 2001 Nov;16(2):133-7.
Autocrine regulation of prolactin secretion by endothelins: a permissive role for estradiol.

Kanyicska B, Sellix MT, Freeman ME.

Program in Neuroscience, Department of Biological Science, Florida State University, Tallahassee 32306-4340, USA. beleuro.fsu.edu

We have previously found that lactotrophs express and secrete endothelin-like peptides that influence prolactin (PRL) secretion in an autocrine fashion. We have also observed that the incidence of endothelin-immunoreactive lactotrophs is markedly affected by ovarian steroids. In this study, we examined how the ovarian steroid background determines the efficiency of the endothelin-mediated autocrine feedback regulation of PRL secretion. Ovariectomized adult female rats were used throughout these studies. Steroid replacements were made by sc implantation of Silastic capsules immediately following ovariectomy. Eight to 10 wk later, three animals from each treatment group (no steroid control, estradiol, progesterone, estradiol plus progesterone) were sacrificed by decapitation, and the anterior pituitary cells were enzymatically dispersed using collagenase and hyaluronidase. A PRL-specific reverse hemolytic plaque assay was used to measure PRL secretion at the single-cell level. BQ123, a synthetic cyclic pentapeptide with distinctive endothelin-A receptor antagonist quality, caused only a modest elevation of PRL secretion in the control group. Endothelin antagonism did not affect PRL secretion in cells obtained from progesterone-implanted animals. Endothelin antagonism did, however, increase overall PRL secretion in the estradiol and estradiol plus progesterone groups by five- and threefold, respectively. Frequency distribution of PRL plaques in these same two BQ123-treated groups revealed two subpopulations, indicating that lactotrophs differ in their response to endogenous endothelin feedback and that this difference is steroid dependent. These observations clearly suggest that the ovarian steroi




J Lipid Res. 2002 Mar;43(3):392-7.
LCAT facilitates transacylation of 17 beta-estradiol in the presence of HDL3 subfraction.

Hockerstedt A, Tikkanen MJ, Jauhiainen M.

Department of Medicine, Helsinki University Central Hospital, FIN-00290, Helsinki, Finland.

It has been shown that estrogens need to be metabolized to their hydrophobic estrogen ester derivatives to act as antioxidants in lipoproteins. Data suggest that 17beta-estradiol (E(2)) becomes esterified in LCAT-induced reactions and the esters are transported from HDL particles to LDL and VLDL particles by a CETP-dependent mechanism. In the present study we have further investigated the regulation of E(2) esterification by LCAT and focused on the importance of HDL structure and composition in the esterification process. Isolated LDL, HDL(2), HDL(3), and reconstituted discoidal HDL (rHDL) were incubated with labeled E(2), with and without purified LCAT, at 37 degrees C for 24 h. After purification of the lipoprotein fractions, there was a significant peak of radioactivity representing esterified estradiol attached to HDL(3) and rHDL, but HDL(2) and LDL contained only trace amounts of labeled estradiol ester. TLC analysis confirmed that the radioactivity migrated in a position corresponding to that of 17beta-E(2) 17-monoester standard. The amount of radioactivity associated with HDL(3) and rHDL representing esterified E(2) was significantly increased by addition of purified LCAT. However, only limited increases of radioactivity were observed in HDL(2) and LDL. In conclusion, HDL subfractions differ in their potential to regulate estradiol esterification by LCAT.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11893775&dopt=Abstract estradiol




Biol Reprod. 2001 Dec;65(6):1634-9.
Estradiol-17beta is produced in bovine corpus luteum.

Okuda K, Uenoyama Y, Berisha B, Lange IG, Taniguchi H, Kobayashi S, Kobayashi S, Miyamoto A, Schams D.

Laboratory of Reproductive Endocrinology, Faculty of Agriculture, Okayama University, Okayama 700-8530, Japan. kokudc.okayama-u.ac.jp

The aim of this study was to investigate the expression of cytochrome P450 aromatase (aromatase) mRNA, its activity, and estradiol-17beta (estradiol) secretion in bovine corpus luteum (CL) during the estrous cycle. Expression of aromatase mRNA was examined in CL at the early, mid, late, and regressed luteal stages by using a reverse transcription-polymerase chain reaction. Aromatase mRNA was detected in all luteal stages examined, although aromatase expression was significantly lower during the early and regressed luteal phases compared to the mid and late luteal phases. Moreover, cultured midluteal cells clearly converted exogenous [(3)H]androstenedione into estradiol, and an aromatase inhibitor significantly inhibited this conversion. To characterize the local release of estradiol within the CL during the estrous cycle, an in vitro microdialysis system (MDS) of CL was conducted. Estradiol in MDS perfusate was confirmed by a reverse-phase high-performance liquid chromatography in combination with enzyme immunoassays. Basal release of estradiol from microdialyzed CL did not change during the estrous cycle. Additionally, when freshly prepared midluteal cells were exposed to estradiol (10(-14) to 10(-9) M), estradiol stimulated prostaglandin (PG) F(2alpha) secretion (P < 0.05), although it did not affect progesterone and oxytocin secretion. The overall results indicate that estradiol is produced locally in bovine CL throughout the estrous cycle, and they suggest that estradiol plays a role in regulating PGF(2alpha) production in CL as an autocrine/paracrine factor.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11717122&dopt=Abstract estradiol




J Natl Cancer Inst. 2001 Nov 21;93(22):1714-23.
Effect of long-term estrogen deprivation on apoptotic responses of breast cancer cells to 17beta-estradiol.

Song RX, Mor G, Naftolin F, McPherson RA, Song J, Zhang Z, Yue W, Wang J, Santen RJ.

Department of Internal Medicine, University of Virginia School of Medicine, Charlottesville, USA.

BACKGROUND: High doses of estrogen can promote tumor regression in postmenopausal women with hormone-dependent breast cancer, but the mechanism is unknown. We investigated the molecular basis of this process by using LTED cells, which were derived by growing MCF-7 breast cancer cells under long-term (6-24 months) estrogen-deprived conditions. METHODS: We treated LTED and MCF-7 cells with various concentrations of 17beta-estradiol (estradiol) and assayed their growth by counting the cells and measured apoptosis by annexin V staining and DNA fragmentation. Using western blot analysis, we also examined the expression of the apoptosis-inducing system of the Fas death receptor protein and its ligand, FasL, in these cells. To assess the involvement of Fas and FasL in the induction of apoptosis in LTED cells, we used activating anti-Fas antibodies and the universal caspase inhibitor Z-VAD. Finally, we examined the expression of Fas protein in E8CASS and BSK3 cells, two other cell lines derived by depriving MCF-7 cells of estrogen long term, and the responses of these cells to high-dose estradiol. All statistical tests were two-sided. RESULTS: High concentrations of estradiol (>or=0.1 nM) resulted in a statistically significant, 60% reduction in the growth of LTED cells (P< .001) and in a sevenfold increase in apoptosis (P< .001) as compared with levels in vehicle-treated cells. Both LTED and MCF-7 cells expressed FasL, but only LTED cells expressed Fas. Treatment of LTED cells with 0.1 nM estradiol increased the expression of FasL. Activating anti-Fas antibodies increased apoptosis of LTED cells, which was further stimulated by estradiol. Z-VAD blocked estradiol-i




Mutagenesis. 2003 May;18(3):243-7.
Increased cell proliferation is associated with genomic instability: elevated micronuclei frequencies in estradiol-treated human ovarian cancer cells.

Stopper H, Schmitt E, Gregor C, Mueller SO, Fischer WH.

Department of Toxicology, University of Wurzburg, Versbacher Strasse 9, D-97078 Wurzburg, Germany.

Estrogen-related cancers are often associated with the hormone's tumor promoting activity. Recently, estradiol has also been demonstrated to induce gene mutations in the physiological concentration range. Mitotic disturbances are found at higher concentrations. In the present study we demonstrate data suggesting an additional mechanism for the induction of genetic damage, i.e. chromosomal breakage. Estrogen receptor-positive (BG-1) and -negative (UCI) human ovarian cancer cell lines were investigated for micronucleus formation after treatment with estradiol. BG-1 cells but not UCI cells showed an increase in micronucleus formation which correlated with the estradiol-induced cell proliferation. The specific estradiol receptor antagonist hydroxytamoxifen suppressed the formation of micronuclei in BG-1 cells. Increased micronucleus frequencies were also seen after normalization of the data to the number of cell divisions. Kinetochore analysis revealed a difference between micronuclei induced by picomolar concentrations of estradiol (kinetochore-negative) and micromolar concentrations (predominantly kinetochore-positive) leading to mitotic disturbances. In accordance with this finding, analysis of the cell cycle revealed decreased cell numbers in G(2)/M phase after treatment with picomolar concentrations, usually not found after mitotic disturbances. We hypothesize that hormone-specific forcing of responsive cells through the cell cycle leads to an override of checkpoints operating under homeostatic control of the cell cycle, resulting in genomic instability.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12714689&dopt=Abstract estradiol




Life Sci. 2001 Oct 26;69(23):2811-7.
Hydrocortisone modulates the effect of estradiol on endothelial nitric oxide synthase expression in human endothelial cells.

Xu R, Sowers JR, Skafar DF, Ram JL.

Department of Physiology, Wayne State University, Detroit, MI 48201, USA.

The interaction between hydrocortisone and estradiol on the regulation of endothelial nitric oxide synthase (eNOS) expression was investigated in human umbilical vein endothelial cells (HUVECs). Following incubation in medium containing dextran-coated-charcoal-stripped serum (DCC-stripped medium) for 4 days, incubation of HUVECs with 0.1 nM estradiol for 24 hr in the absence of hydrocortisone increased levels of eNOS mRNA measured by ribonuclease protection assay above control (0 nM estradiol). 2 microM hydrocortisone applied for 24 hr preceding and during estradiol application inhibited the estradiol-elicited increase in eNOS mRNA levels, reducing mRNA levels from 134% +/- 14% of control to 85% +/- 5% of control. Significant (ANOVA, p<0.01) reductions of estradiol-mediated increases of mRNA levels occurred over a range of hydrocortisone concentrations (10 nM, p<0.05; 2 microM, p<0.05; n=3-12). In the presence of 2 microM hydrocortisone, 10 nM estradiol significantly reduced eNOS mRNA levels to 59% +/- 3% of control. The ability of hydrocortisone to block or reverse the estradiol-mediated increase in eNOS mRNA levels may provide a link between elevated hydrocortisone levels and decreased NO production, potentially contributing to the development of hypertension and cardiovascular disease in vivo and antagonizing cardioprotective effects of estrogens.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11720085&dopt=Abstract estradiol




Int J Fertil Womens Med. 2001 Sep-Oct;46(5):265-70.
Effects of two oral contraceptives, containing 30 or 20 microg of ethinyl estradiol in combination with gestodene, on blood coagulation and fibrinolysis in Brazilian women.

Ferreira AC, Montes MB, Franceschini SA, Toloi MR.

Department of Clinical, Toxicological and Bromatological Analysis, Faculty of Pharmaceutical Sciences of Ribeirao Preto, University of Sao Paulo, Brazil.

OBJECTIVE: Blood coagulation and fibrinolytic variables were evaluated in 46 Brazilian women treated with either of two monophasic oral contraceptives (OC), containing 30 or 20 microg of ethinyl estradiol, and 75 microg of gestodene. METHODS: The effects on procoagulants, anticoagulants, pro-fibrinolytics and antifibrinolytics and fibrin turnover were evaluated after treatment for six consecutive cycles, the impact of reduction of ethinyl estradiol dosage on these effects being assessed. RESULTS: The OC containing 30 microg of ethinyl estradiol significantly increased the activities of factors VIII and X, whereas the one containing 20 microg of ethinyl estradiol caused no changes in clotting factors. Neither treatment altered fibrinogen levels or factor VII, IX or XII activity. There were no changes in antithrombin levels, but treatment with 30 microg ethinyl estradiol increased protein C levels and treatment with 20 microg decreased total protein S levels. Concerning the fibrinolytic parameters, both OCs increased plasminogen activity, whereas no changes in PAI-1, t-PA, alpha-2-antiplasmin or fibrin degradation products were observed. The reduction in ethinyl estradiol dosage from 30 microg to 20 microg eliminated the effects on factors VIII and X. CONCLUSIONS: The results show that the OC studied did not cause sufficient changes to indicate that there may be a correlation between these laboratory alterations and clinical results. The lack of reports concerning the hemostatic effects of OCs on Brazilian women hinders comparison of the present data with those obtained for other et




Endocrine. 2001 Jul;15(2):165-75.
Effect of estradiol, diethylstilbestrol, and resveratrol on F0F1-ATPase activity from mitochondrial preparations of rat heart, liver, and brain.

Kipp JL, Ramirez VD.

Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana 61801, USA. liuiuc.edu

The question of whether estrogens or estrogen-like compounds would alter differentially the enzymatic activity of the FOF1-ATPase was addressed. Mitochondrial fractions of the liver, brain, and heart were obtained from adult male rats and solubilized by digitonin. About 85% of the adenosine triphosphate hydrolysis by these three preparations come from the mitochondrial FOF1-ATPase. The enzymatic activity differed in the following order: liver < brain < heart. A concentration of 13 nM estradiol stimulated the FOF1-ATPase activity in heart by 10% (p < 0.01), but not in liver or brain. 17beta-estradiol competed off the binding of estradiol-17beta-17-(O-carboxymethyl)oxime:125I-labeled bovine serium albumin to mitochondrial preparations of the heart, revealing two binding sites. Resveratrol inhibited the F0F1-ATPase activity in both heart and liver with an IC50 of 13-15 microM, which confirmed our previous report in preparations of brain. Lower doses (picomolar to nanomolar) of resveratrol stimulated the FOF1-ATPase activity in liver by 10% but not in heart. At 6.7 microM, diethylstilbestrol (DES) inhibited the FOF1-ATPase activity in the three preparations by 61-67%. This study demonstrates that estradiol activates rat heart mitochondrial FOF1-ATPase at physiologic concentrations and that the FOF1-ATPase activity is markedly different in rat liver, brain, and heart. In addition, estradiol, DES, and resveratrol alter the FOF1-ATPase activity selectively, probably via different mechanisms.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11720242&dopt=Abstract estradiol




J Neuroendocrinol. 2001 Dec;13(12):1051-8.
Oestradiol microimplants in the ventromedial preoptic area inhibit secretion of luteinizing hormone via dopamine neurones in anoestrous ewes.

Anderson GM, Connors JM, Hardy SL, Valent M, Goodman RL.

Department of Physiology, West Virginia University, Morgantown, West Virginia 26506, USA.

Oestradiol exerts a season-specific negative feedback effect on the GnRH/LH neurosecretory system of the Suffolk ewe. This neuroendocrine suppression is mediated in part by dopamine A15 neurones, but these neurones do not possess the oestrogen receptor. Based on indirect evidence, we hypothesized that oestrogen receptor-containing neurones in the ventromedial preoptic area (vmPOA) may be the initial step in a neuronal system whereby oestradiol suppresses GnRH secretion during the non-breeding season. To test this, three experiments were conducted using ovariectomized ewes receiving either empty or oestradiol-containing bilateral microimplants directed at the vmPOA or s.c. subcutaneous oestradiol-containing implants. In the first experiment, LH pulse frequency was measured on days 0, 1, 7 and 14 of treatment during seasonal anoestrus. In vmPOA oestradiol and s.c. oestradiol groups only, LH pulse frequency was suppressed on days 7 and 14, with maximal suppression evident by day 7. In the second experiment, this protocol was repeated during the breeding season, with LH pulses examined on days 0 and 7; LH pulse frequency did not change in any group. The third experiment tested if the effect of vmPOA oestradiol during anoestrus could be overcome by an injection of the dopamine-D2 receptor antagonist (-)-sulpiride. The vmPOA microimplants and s.c. oestradiol implants again suppressed LH pulse frequency and this was reversed by sulpiride in vmPOA oestradiol ewes. We conclude that oestradiol acts on cells in the vmPOA to stimulate a system involving dopamine neurones that inhibits GnRH/LH pulsatility in the anoestrous ewe.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11722701&dopt=Abstract estradiol [PubMed - indexed for MEDLINE]<