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PubMed2004

'Pulsed' estradiol action can stimulate breast cancer cell proliferation.

PURPOSE OF INVESTIGATION: The newly available nasal estradiol application serum concentrations measure up to 10-fold higher compared to common hormone replacement therapy (HRT). Since this has only a short-time peak it has been suggested that breast cancer risk may be reduced, because of lower activation of the estradiol-receptor-transcription cascade. METHODS: Estradiol was tested at 10(-9) and 10(-8) M corresponding to the serum levels achieved with nasal application. In addition also comparable exposure times were investigated: Incubation time was 10, 20, 40, 60 and 180 min every day for four days, compared with continuous non-stop incubation for four days. The well-recognized MCF-7 breast cancer cell line was used. Cell proliferation was measured by the ATP-assay. RESULTS: Estradiol in concentrations achieved with 'pulsed' HT was able to elicit proliferation of MCF-7 cells already after an incubation time of ten minutes which correlates with the minimum of exposure time using nasal estradiol application. Compared to non-stop continuous estradiol added in the same high concentrations over four days no significant differences were observed. CONCLUSIONS: Short-time application of estradiol is able to stimulate breast cell proliferation to the same degree as continuously administered estradiol in high concentrations. Thus it remains questionable, if a 'pulsed' estradiol therapy may reduce breast cancer risk during HRT. Clinical studies are urgently needed to reveal the breast cancer risk during nasal estradiol application especially since this risk might be increased depending on the concentrations used.

Administration, Intranasal↗
PubMed2005

Acute effects of 17beta-estradiol on oxidative stress in ischemic rat striatum.

Changes in the extracellular concentrations of monoamines, their metabolites, and hydrogen peroxide in the rat striatum during middle cerebral artery (MCA) occlusion and reperfusion were investigated by a microdialysis procedure, and the effects of 17beta-estradiol and tamoxifen (an antagonist of estrogen receptors) on them were evaluated. Male Wistar rats were randomly divided into four groups: saline-treated animals, 17beta-estradiol-treated animals, saline-plus-tamoxifen-treated animals, and 17beta-estradiol-plus-tamoxifen-treated animals. Sixty minutes after an intracerebroventricular injection of saline (20 microL) or 17beta-estradiol (150 microg/20 microL), all animals were subjected to 15-minute MCA occlusion under anesthesia. Tamoxifen (1.5 mg) or vehicle was intravenously administered 30 minutes before the saline or 17beta-estradiol treatment. Microdialysis samples in the striatum were collected every 15 minutes, and concentrations of monoamines, their metabolites, and hydrogen peroxide were determined. Delayed neuronal death in the striatal neurons was observed after 7 days by light microscopy. Administration of 17beta-estradiol reduced neuronal damage caused by focal ischemia. Tamoxifen did not affect the improvement by 17beta-estradiol. Although transient ischemia produced a marked increase in the dopamine level, there were no differences in the peak level among the groups. The level of hydrogen peroxide was increased after reperfusion in the saline group. The level in the 17beta-estradiol group was suppressed before induction of ischemia, and no increase was observed by ischemia. Tamoxifen did not affect the suppression of the increase by 17beta-estradiol. Acute treatment with 17beta-estradiol showed a protective effect against ischemia-reperfusion injury. Antioxidant effects of the agent may be a predominant mechanism underlying the protection.

Animals↗
PubMed2005

Hormone replacement with estradiol: conventional oral doses result in excessive exposure to estrone.

BACKGROUND: There is a lack of consensus about the safety of estrogen replacement therapy, especially with regard to its impact on a woman's risk for breast cancer. Elevated urinary or serum estrone and estradiol concentrations in postmenopausal women are associated with a moderately elevated risk of breast cancer. METHODS: Twenty-four-hour urinary steroid hormone profiles, including the measurement of estrone, estradiol, and estriol, were conducted for 35 postmenopausal women receiving oral estradiol at doses from 0.025-2.0 mg/day. RESULTS: Urinary excretion of estradiol exceeded premenopausal reference range values in women taking estradiol at doses greater than 0.5 mg/day. Urinary estrone excretion exceeded premenopausal reference range values in women taking estradiol doses of 0.25 mg/day or higher. Literature data indicate serum estrone concentrations also markedly exceed premenopausal reference ranges when estradiol is administered orally at a dose of 1 mg/day. CONCLUSIONS: The previously recommended oral dose of estradiol (1-2 mg/day) results in urinary excretion of estrone at values 5-10 times the upper limit of the reference range for premenopausal women. Retrospective studies associating oral estradiol with increased risk of breast cancer may reflect overdose conditions. Based on current knowledge, a prudent dose ceiling for oral estradiol replacement therapy of 0.25 mg/day is proposed.

Administration, Oral↗
PubMed2006

[Effects of estradiol intervention on peripheral blood CD90+ cells and cardiac function in de-ovary rats before and after myocardial infarction].

AIM: To investigate the effects of estradiol intervention on peripheral blood CD90+ cells and cardiac function in de-ovary rats before and after myocardial infarction. METHODS: Thirty SD female rats were divided into the control group, acute myocardial infarction group, de-ovary myocardial infarction group, de-ovary replacement group with estradiol, and de-ovary therapy group with estradiol. CD90+ cell percentage was determined with flow cytometry. The left ventricle end systolic pressure (LVESP), left ventricle end diastolic pressure (LVEDP), +dp/dt(max) and -dp/dt(max) were also measured with the POWERLAB4.12 system. RESULTS: The percentage of peripheral blood CD90+ cells in the de-ovary myocardial infarction group was remarkably lower than that in the acute myocardial infarction group and the de-ovary replacement group with estradiol (P<0.01). In the de-ovary replacement group with estradiol, the percentage of peripheral blood CD90+ cells was remarkably elevated following the first day of operation (P<0.05), reaching the peak value at day 3. In the de-ovary therapy group with estradiol, it started to elevate at day 7 after the operation, much lower than that in the de-ovary replacement group with estradiol. LVESP in each operation group decreased, especially in the acute myocardial infarction group, whereas LVEDP increased in the de-ovary group and de-ovary therapy group with estradiol (P<0.01). CONCLUSION: Replacement with estradiol before myocardial infarction exerts more beneficial effects than estradiol replacement after myocardial infarction in de-ovary rats.

Animals↗
PubMed1991

Dopamine receptor reappearance after irreversible receptor blockade: effect of chronic estradiol treatment of ovariectomized rats.

It is well established that estrogen modulates central dopamine functions; however, the mechanism of this interaction is still poorly understood. We have used peripheral N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) administration to induce irreversible blockade of dopamine receptors in ovariectomized female rats, which were pretreated with estradiol (10 micrograms, twice each day for 2 weeks) or its vehicle, in order to investigate the effect of estradiol on dopamine receptor repopulation kinetics. As previously observed, chronic estradiol treatment increased both striatal D1 and D2 dopamine receptor densities and left affinities unchanged. Anterior pituitary D2 dopamine receptor density remained unchanged. One day after EEDQ administration, a similar decrease (80%) of [3H]SCH 23390 and [3H]spiperone binding to striatum of estradiol- and vehicle-treated animals was observed. Anterior pituitary D2 dopamine receptor specific binding was reduced by about 50% the day after EEDQ. Recovery after EEDQ administration showed that both receptor production rate and degradation rate constants of anterior pituitary D2 and striatal D1 receptors were slowed after chronic estradiol treatment, whereas recovery rates for striatal D2 dopamine receptors were unaffected. EEDQ administration in vehicle-treated rats did not significantly affect plasma prolactin levels, whereas the combination of estradiol pretreatment and EEDQ administration led to increased plasma prolactin levels, compared with estradiol-treated animals that did not receive EEDQ. This suggests that only a fraction of anterior pituitary dopamine receptors are required for a maximal inhibition of prolactin secretion. Estradiol affected both striatal D1 and D2 dopamine receptor densities but only D1 dopamine receptor repopulation kinetics, suggesting that it may act by different mechanisms on each dopamine receptor. Alternatively, estradiol may affect dopamine receptor interaction. Thus, the present study raises the possibility that a biochemical D1/D2 receptor interaction affects dopamine receptor biosynthesis, turnover, and/or gene expression and that estradiol may influence this dopamine receptor interaction in the striatum.

Adrenergic alpha-Antagonists↗
PubMed1990

Estradiol sensitivity test using contact-sensitive plates of confluent BALB/c 3T3 cell monolayers.

We have attempted to develop an in vitro assay system for predicting estradiol sensitivity of clinical cancer cells by measuring the effects of estradiol on the net DNA synthesis of primary culture cells. Superinoculation of neoplastic and normal cells onto confluent monolayers of a contact-sensitive cell line, which have been designated as contact-sensitive plates (CSPs), resulted in both the specific growth of the neoplastic cells and the growth inhibition of contact-sensitive normal cells. The applicability of CSPs to an estradiol sensitivity test was examined in the known estradiol-sensitive, estrogen receptor-possessing cell lines, MCF-7 breast cancer and KSE-1 esophageal cancer cells. The responses of each cancer cell to estradiol were sufficiently evaluated in this assay and clearly demonstrated stimulative and inhibitive growth regulatory effects of the estradiol in MCF-7 and KSE-1 cells, respectively. A total of 38 clinical carcinomas (33 of the breast and 5 of the esophagus) were tested for their estradiol sensitivity. A statistically significant increase of cancer cell growth (P less than 0.1) in nontreated culture from the 48th to the 96th h of the primary culture on CSPs was observed in 28 of 38 overall cases (73.7%), and the evaluable data were obtained within 5 days by a sampling of 5 X 10(3) cancer cells. Most of the breast carcinomas exhibited a positive correlation between the growth-stimulative effect of estradiol in this assay and the estrogen receptor levels in the resected specimens. On the other hand, a clinical case of esophageal cancer with an estrogen receptor showed a growth inhibition of primary carcinoma cells by estradiol treatment. These results therefore indicate the feasibility of predicting individual tumor response to estradiol by using a rapid sensitivity test in vitro.

Animals↗
PubMed1984

Estradiol regulation of secretory component in the uterus of the rat: evidence for involvement of RNA synthesis.

The present studies were undertaken to characterize the response of uterine secretory component (SC) to estradiol. Administration of estradiol for 3 days to ovariectomized rats before incubation of uterine tissues resulted in a marked accumulation of SC in the incubation media. When uteri from ovariectomized rats treated with progesterone or testosterone were incubated, very little SC accumulated in the media, indicating that the estradiol-stimulated increase is hormone-specific. When uteri from rats that received estradiol for 6 days were compared with uteri from 3-day treated rats, SC release during a 24-hr incubation period was the same. This finding indicates that in the presence of prolonged estradiol exposure, SC production continues. The estradiol-induced accumulation of SC in culture is not due to the release of pre-formed uterine SC. When tissue SC levels were measured after 3 days of estradiol treatment, very little tissue SC was found relative to that released into culture media during 24 hr of incubation. The addition of actinomycin D to the incubation media markedly inhibited SC release by uteri from estradiol-treated rats. The release of SC was also inhibited by alpha-amanitin, a known inhibitor of Type II polymerase. These studies demonstrate that estradiol stimulation of SC is markedly reduced by inhibitors of RNA synthesis, and suggest that estradiol regulation of SC is mediated through uterine mRNA synthesis.

Animals↗
PubMed1983

Effect of estradiol on human breast cancer cells in culture.

Conditions are described for growing and maintaining the estradiol sensitivity of the human breast cancer cell line ZR-75-1 both in monolayer and suspension cultures. Either newborn calf or fetal calf serum can be used in the culture medium, but an effect of estradiol on growth of the cells was only observed reproducibly if the serum was first treated with dextran-charcoal. Sulfatase treatment of the sera prior to dextran-charcoal treatment did not decrease cell growth in the absence of added estradiol, indicating that estrogen sulfates are unlikely to contribute to cell growth in dextran-charcoal-treated sera. In monolayer cultures, estradiol increased both the growth rate and final saturation density of the cells for each individual plating density tested in a dose-dependent manner with maximal stimulation occurring between 10(-10) and 10(-8) M estradiol. Estradiol also markedly increased the ability of the cells to grow both in suspension and semisolid Methocel cultures. In suspension, the cells grew as tight balls which clustered together to give small organoid-like structures reaching diameters of 4 mm and composed of an outer shell of living cells containing a central cavity of necrotic cells. In the absence of estradiol in both monolayer and suspension, the cells went through a limited and constant number of divisions and then stopped, such that the final cell number was determined by the initial plating density. In the presence of estradiol, this block was removed such that in monolayer cultures the final cell number was independent of plating density. A major loss of estradiol response was found if the cells were grown for 7 to 14 days in the absence of estradiol. This loss of response appeared to be due to a loss of ability to grow rather than to selective cell death within the population.

Breast Neoplasms↗
PubMed1993

Ethinyl estradiol decreases acidification of rat liver endocytic vesicles.

Treatment with ethinyl estradiol is known to impair bile formation, bile acid transport and Na,K-ATPase activity, to alter receptor-mediated endocytosis and transcytosis of IgA and asialoorosomucoid and to affect membrane lipid composition and fluidity. Because appropriate sorting and trafficking of asialoorosomucoid requires adequate acidification of endocytic vesicles by a lipid-sensitive electrogenic proton pump, we examined the effects of 5 days of treatment with ethinyl estradiol (5 mg/kg body wt, subcutaneously) on acidification of early endosomes prepared from male rat livers. Littermate control animals received equal volumes of the solvent propylene glycol. Pretreatment with ethinyl estradiol reduced ATP-dependent initial rates of endosome acidification by 11% to 25% when measured in potassium medium containing 0 to 140 mmol/L chloride; these differences were significant at four of six chloride concentrations tested. The proton pumps of ethinyl estradiol and propylene glycol endosomes exhibited similar Michaelis-Menten constants for MgATP (Michaelis-Menten constant of 63 and 66 mumol/L in the absence of chloride and 101 and 126 mumol/L in the presence of chloride, respectively). Acidification of ethinyl estradiol and propylene glycol endosomes changed in the same manner when various cations or anions were substituted for potassium gluconate, although the effects of ethinyl estradiol were less marked in the absence of K+. Kinetics of inhibition for ethinyl estradiol and propylene glycol endosomes were similar for the proton pump inhibitors N-ethylmaleimide (50% inhibitory concentrations of 13.5 and 18.1 mumol/L), dicyclohexylcarbodiimide (50% inhibitory concentrations of 206 and 216 mumol/L) and bafilomycin A (50% inhibitory concentrations of 11 and 6 nmol/L). Although initial rates of acidification were slower in ethinyl estradiol endosomes, ATP-dependent steady-state vesicle interior pH was the same as that of propylene glycol endosomes over a range of chloride concentrations; this appeared to be due mainly to a trend toward decreased proton leak rates in ethinyl estradiol endosomes. Overall, ethinyl estradiol treatment modestly decreased initial rates of acidification and vesicle proton leakage, perhaps because of changes in endosome lipid composition; differences in the number, density or activation state of proton pumps; or differences in endosome geometry. Because the decrease in acidification rates was small, the effects of estrogen on the efficiency of uncoupling of endocytosed ligands such as asialoorosomucoid from their receptors in early endosomes; thus the rates of sorting and distribution of ligands remain unclear.

Adenosine Triphosphate↗
PubMed1996

Estradiol reduces calcium currents in rat neostriatal neurons via a membrane receptor.

Until recently, steroid hormones were believed to act only on cells containing intracellular receptors. However, recent evidence suggests that steroids have specific and rapid effects at the cellular membrane. Using whole-cell patch-clamp techniques, 17 beta-estradiol was found to reduce Ba2+ entry reversibly via Ca2+ channels in acutely dissociated and cultured neostriatal neurons. The effects were sex-specific, i.e., the reduction of Ba2+ currents was greater in neurons taken from female rats. 17 beta-Estradiol primarily targeted L-type currents, and their inhibition was detected reliably within seconds of administration. The maximum reduction by 17 beta-estradiol occurred at picomolar concentrations. 17 beta-Estradiol conjugated to bovine serum albumin also reduced Ba2+ currents, suggesting that the effect occurs at the membrane surface. Dialysis with GTP gamma S prevented reversal of the modulation, suggesting that 17 beta-estradiol acts via G-protein activation. 17 alpha-Estradiol also reduced Ba2+ currents but was significantly less effective than 17 beta-estradiol. Estriol and 4-hydroxyestradiol were found to reduce Ba2+ currents with similar efficacy to 17 beta-estradiol, whereas estrone and 2-methoxyestriol were less effective. Tamoxifen also reduced Ba2+ currents but did not occlude the effect of 17 beta-estradiol. These results suggest that at physiological concentrations, 17 beta-estradiol can have immediate actions on neostriatal neurons via nongenomic signaling pathways.

Animals↗
PubMed1998

In vitro effect of estradiol, progesterone, testosterone, and of combined estradiol/progestins on low density lipoprotein (LDL) oxidation in postmenopausal women.

OBJECTIVE: One of the mechanisms currently proposed to explain the cardioprotective effect of hormone replacement therapy (HRT) is the antioxidative property of estrogens. Considering that HRT involves the administration of an estrogen, usually combined with a progestin and sometimes with an androgen, we investigated the following in vitro: (1) the effect of estradiol, progesterone, and testosterone on the oxidation of low density lipoprotein; (2) the possible pro-oxidative effect of progesterone and testosterone on native low density lipoprotein; and (3) the possible modification of the antioxidant effect of estradiol on low density lipoprotein induced by progestins. DESIGN: Low density lipoprotein was isolated from blood samples obtained from 20 untreated postmenopausal women and divided in multiple aliquots, each containing 0.5 mg LDL protein. In Protocol 1 (n = 10) different doses of estradiol, progesterone, and testosterone ranging from 0 to 26 micrograms/ml were tested inducing oxidation with 15 microM copper sulfate. In Protocol 2 (n = 6) we studied the rate of oxidation of low density lipoprotein incubated with progesterone or testosterone without any oxidative induction. In Protocol 3 (n = 10) we studied the concomitant effect of 15 microM estradiol with four separate progestins (progesterone, medroxyprogesterone acetate, norethindrone, and norgestrel) in different doses (0, 5, 15, and 50 microM). After incubation for 4 h at 37 degrees C, malonaldehyde was measured as a marker of low density lipoprotein oxidation. The results were expressed in mean +/- SD. RESULTS: Protocol 1: Estradiol induced a dose-dependent decrease in malonaldehyde generation, from a baseline of 61.8 +/- 30.2 nmol/mg protein to 11.6 +/- 7.1 nmol/mg protein at the highest dose of estradiol tested (p < 0.0001). Progesterone or testosterone did not modify malonaldehyde generation. Protocol 2: Progesterone and testosterone did not show pro-oxidative action. Protocol 3: Estradiol 15 microM alone induced a 35% decrease in malonaldehyde generation, from a baseline of 75.4 +/- 25.4 to 49.3 +/- 18.8 nmol/mg protein (p < 0.0001). Norgestrel and norethindrone did not modify the antioxidant effect of estradiol (p > 0.05). Progesterone and medroxyprogesterone acetate induced a further reduction of malonaldehyde concentration to 37.2 +/- 20.8 and 38.6 +/- 18.2 nmol/mg protein, only at the highest dose tested (p < 0.02 and p < 0.01, respectively). CONCLUSIONS: Our results demonstrate that, in contrast with the potent antioxidant effect of estradiol, progesterone and testosterone did not show any pro- or antioxidant effect on low density lipoprotein in vitro. Furthermore, progestins did not counteract the antioxidant effect of estradiol in vitro.

Copper Sulfate↗
PubMed1999

Estradiol accelerates extinction of a conditioned taste aversion in female and male rats.

Exogenous testosterone treatment prolongs extinction of conditioned taste aversions and estradiol treatment prevents testosterone from prolonging extinction in both gonadectomized males and females. Estradiol could require the presence of testosterone for its effect or its action alone could accelerate extinction. The first series of experiments were designed to test the hypothesis that estradiol accelerates extinction when it is given in the absence of testosterone. The results showed that estradiol accelerates extinction of conditioned taste aversions in the absence of testosterone in gonadectomized Sprague-Dawley females and Fischer 344 females and males. The second series of experiments were designed to determine whether estradiol and testosterone differ in the temporal requirements for their opposite effects on extinction. The results showed that estradiol can accelerate extinction when it is present before and during acquisition (from 8 days before until 3 days after acquisition) or when it is present before and during extinction (from 2 days after acquisition, which was 23 days before extinction, until extinction trials were terminated). This is in contrast to a previous finding that testosterone prolongs extinction only when it is present before and during extinction. The following two hypotheses were suggested to account for the temporal effects of estradiol on extinction of conditioned taste aversions: (1) the presence of estradiol during acquisition reduces the effectiveness of LiCl through its action on the opioid system, and the presence of estradiol during extinction activates a neural pathway, such as that associated with activity levels, that accelerates extinction of passive avoidance tasks in general or (2) the presence of estradiol before, not during, acquisition or extinction accelerates extinction because of its illness-inducing properties. Most of the evidence supports the second hypothesis.

Animals↗
PubMed1987

The effect of exogenous estradiol on litter size in a typical swine herd.

Fifty-six female pigs (12 gilts, 26 primiparous and 18 multiparous sows) were bred and assigned to receive either corn oil (vehicle; n=28) or estradiol-17beta (2 mg/day; i.m.; n=28) on Days 12 and 13 (Day 0=first day of estrus) to determine if exogenous estradiol could improve litter size in swine. Though litter size of the females farrowing was not increased with estradiol treatment (vehicle versus estradiol, 9.7+/-0.8 versus 10.1+/-1.8 live pigs born, respectively), more females in this group remained pregnant (vehicle versus estradiol, 6 versus 1 recycled, respectively; P<0.05). Litter size, expressed as the number of pigs born per-female-bred, was therefore increased with exogenous estradiol (vehicle versus estradiol, 7.6+/-0.8 versus 9.8+/-0.7 live pigs born, respectively; P<0.05). Some of these estradiol- treated females produced smaller (P<0.05) litters and this may be of concern in herds experiencing low fertilization/conception rates. Overall 60 more pigs were born alive to females in the estradiol-treated group than to the control group females. This experiment demonstrated that supplemental estradiol treatment on Days 12 and 13 assisted in maintenance of pregnancy and thereby increased litter size on a per-female-bred basis.

Journal Article↗
PubMed2001

Management of the extremely preterm infant: is the replacement of estradiol and progesterone beneficial?

This review presents data to suggest that postnatal estradiol and progesterone replacement therapy may be beneficial in preterm infants. During pregnancy, maternal plasma levels of estradiol and progesterone increase up to 100-fold compared to the nonpregnant status. The fetus is also exposed to these increasing hormone levels. After delivery, estradiol and progesterone levels drop by a factor of 100 within 1 day. Whereas this is a physiological condition for an infant born at term, preterm delivery means withdrawal from the placental supply of these hormones at an earlier developmental stage. Seventy years ago, the idea was raised that preterm infants may benefit from the replacement of estrogens. Studies in which estrogen was injected subcutaneously showed only a slightly better bodyweight gain compared to placebo-treated controls and therefore routine use was not established. The effective treatment of postmenopausal osteoporosis with hormone replacement therapy led to a pilot study of estradiol and progesterone therapy to prevent osteopenia of prematurity. The highest median bone mineral accretion rate was found in the replacement group when the supplementation with calcium and phosphorus was also sufficient. None of the previous studies dealing with estrogen replacement controlled for achieved plasma levels of estradiol in the infants. In our controlled randomised pilot study with 30 preterm infants (15 in each group), we aimed to maintain intra-uterine plasma levels of estradiol and progesterone. Preterm infants with replacement of estradiol and progesterone for 6 weeks postnatally showed trends to higher bone mineral accumulation. In addition, a trend towards a lower incidence of chronic lung disease was found. Neurodevelopmental follow-up showed normal psychomotor development in infants given estradiol and progesterone, whereas the untreated infants (controls) showed a trend towards delayed development. Recent research emphasises that estradiol and progesterone may be important for brain development. Thus, while there is data indicating that postnatal estradiol and progesterone replacement therapy may be beneficial in preterm infants, experience with this new therapy is limited and extensive research is needed to address the potential benefits and to rule out adverse effects.

Estrogen Replacement Therapy↗
PubMed1998

Ovarian activity in women taking an oral contraceptive containing 20 microg ethinyl estradiol and 150 microg desogestrel: effects of low estrogen doses during the hormone-free interval.

OBJECTIVE: We assessed the effect of low ethinyl estradiol doses given during the nominally hormone-free interval of the Mircette (brand of desogestrel/ethinyl estradiol and ethinyl estradiol) contraceptive regimen on ovarian activity. STUDY DESIGN: In a randomized, double-blind study, healthy women received 150 microg desogestrel and 20 microg ethinyl estradiol for 21 days followed by either placebo for 7 days (Mircette/placebo; N = 24) or placebo for 2 days and 10 microg ethinyl estradiol for 5 days (Mircette/ethinyl estradiol; N = 23). RESULTS: During cycles 2 and 3, the Mircette/placebo group had a higher incidence of persistent ovarian follicles (eight subjects versus three subjects) and on average a greater maximum follicle diameter than the Mircette/ethinyl estradiol group. One Mircette/placebo subject probably ovulated in cycle 2, and another had a luteinized unruptured follicle; no such activity was seen in the in the Mircette/ethinyl estradiol group. The study medication was well tolerated, and there were no apparent between-group differences in vaginal bleeding patterns. CONCLUSION: The Mircette regimen, which includes low ethinyl estradiol doses during the hormone-free interval, more effectively suppresses ovarian follicular activity with a low monthly estrogen dose.

Adolescent↗
PubMed1983

Analysis of binding of [3H]Estradiol to the cytosol fraction of rat pancreas: comparison with sites in the cytosol of uterus.

The cytosol fraction of rat pancreas [100,000 X g (for 1 h) supernatant] demonstrated specific but nonsaturable binding of [3H]estradiol in the concentration range of 2-50 X 10(-9) M. Scatchard analysis of specifically bound [3H]estradiol, determined by the isotope dilution technique (competition with excess unlabeled estradiol), indicated a single class of binding sites (approximately 4.4 pmol/mg protein) with an apparent Kd of 5 X 10(-8) M. Such cytosol fractions, prepared from homogenates that contained protease inhibitors, when prelabeled with [3H]estradiol, demonstrated a single sharp eluate peak of radioactivity after Sephadex G-200 chromatography that corresponded to a molecular weight of 120,000. When protease inhibitors were omitted, [3H]estradiol was associated with material of considerably lower molecular weight. Routinely, the protease inhibitors leupeptin (1 mM), phenylsulfonyl fluoride (0.5 mM), and tosylphenylalanylchloromethyl ketone (0.05 mM) were included in the buffer used for homogenizing both the pancreas and uterus. The protein that binds [3H]estradiol in uterus differed from that in pancreas in a number of ways: 1) in the range of 10-20 X 10(-9) M [3H]estradiol, specific binding of the hormone to uterine sites was saturable, and Scatchard analysis indicated a single class of binding sites, (approximately 0.5 pmol/mg protein) having an apparent Kd of 3 X 10(-10) M; 2) the rate constants of dissociation of the [3H] estradiol-bound complexes in pancreas and uterus were 3.1 X 10(-4) sec-1 (t1/2, 37 min) and 8.7 X 10(-5) sec-1 (t1/2, 134 min), respectively; 3) the molecular weight of the estrogen-binding protein in freshly prepared uterine supernatant fractions appeared to be at least 240,000; this was unaltered regardless of whether protease inhibitors were present during initial homogenization of the tissue; and 4) when uterine supernatants prepared in the absence of protease inhibitors were kept at 8 C for 24 h and then analyzed by Sephadex G-200 chromatography, a second peak of [3H]estradiol-binding activity appeared at the same eluate volume as the low molecular weight binding fractions of pancreas. These data suggest that although the binding proteins in pancreas and uterus are different, there may be some common features at the hormone-binding locus.

Animals↗
PubMed1994

Evidence for receptors specific for 17 beta-estradiol and testosterone in chondrocyte cultures.

Recently, sex hormones were shown to stimulate chondrocyte differentiation and matrix protein synthesis in vitro in a sex-specific and maturation-dependent manner. The aim of the present study was to determine whether cytosolic receptors in these cells would specifically bind 17 beta-estradiol and testosterone, and if so, whether binding was gender- and maturation-dependent. Confluent, fourth passage cultures of cells derived from male or female rat costochondral growth zone and resting zone cartilage were homogenized and specific binding of 17 beta-estradiol or testosterone measured in the cytosolic fraction. Scatchard analysis indicated the presence of a high-affinity 17 beta-estradiol receptor (Kd = 4.5 to 8.7 x 10(-11) M), with low binding capacity (3.9 to 11.2 fmol/mg protein). Chondrocytes from female rats were found to have a significantly greater binding capacity for 17 beta-estradiol than chondrocytes from male rats. However, cells from both sexes had binding capacities that were independent of cell maturation. A high-affinity testosterone receptor (Kd = 4.3 to 6.3 x 10(-11) M) with low binding capacity (4.1 to 5.9 fmol/mg protein) was found in both males and females, but no difference in binding capacity was noted, either as a function of gender or stage of cell maturation. Immunohistochemistry using antibodies against 17 beta-estradiol and testosterone and the 17 beta-estradiol nuclear receptor (D-75) confirmed that 17 beta-estradiol and testosterone receptors were present in chondrocytes from both male and female rats. These data demonstrate that chondrocytes from growth zone and resting zone cartilage are capable of binding both 17 beta-estradiol and testosterone. This suggests that these hormones mediate their direct effects on chondrocytes via receptors specific for their appropriate ligand. The sex-specific effects of 17 beta-estradiol may be due to differences in receptor number between chondrocytes derived from female and male rats. In contrast, the sex-specific effects of testosterone may be regulated at the post receptor level since no differences in binding capacity were found between males and females.

Animals↗
PubMed1991

[Inhibition of testosterone metabolism by 17-alpha-estradiol in rat liver slices].

Inhibition of the Testosterone Metabolism in Rat Liver Slices by 17 alpha-Estradiol. The influence of 17 alpha-estradiol (CAS 57-91-0), a hormonally almost inactive isomer of physiological 17 beta-estradiol, on the metabolism of [14C]-labeled testosterone in rat liver slices was investigated. The analysis of extracts from incubates (3.0 ml medium, 100 mg liver slices, 416 nmol [14C]-testosterone, 0.1-30 micrograms 17 alpha-estradiol, 37 degrees C, 30 min) by thin layer chromatography showed, that 30 micrograms of 17 alpha-estradiol inhibited the testosterone turnover in liver slices of female animals. The failure of a significant inhibitory effect in liver slices of male animals is attributed to the known, much smaller total turnover of testosterone in male liver cells. The amount of unchanged 4-en-3-oxo-steroid (testosterone and 4-androstene-3,17-dione) was increased by a factor of 2.65 and 2.25, respectively. With high probability, the inhibition was the result of a decreased hydrogenation of testosterone to dihydrotestosterone (DHT, 17 beta-hydroxy-5 alpha-androstan-3-one), catalyzed by 5 alpha-reductase, since the production rates of DHT and the DHT-transformation metabolites (5 alpha-androstane-3 alpha,17 beta-diol and 5 alpha-androstane-3,17-dione) were significantly lowered (factors: 0.16, 0.61, 0.61, respectively). In further experiments 17 beta-estradiol and 17 alpha-ethinylestradiol could be shown to inhibit the testosterone turnover in liver slices of female rats, too, but to a lower extent that 17 alpha-estradiol (relative inhibitory effects: 17 alpha-estradiol:17 beta-estradiol:17 alpha-ethinylestradiol = 100 : 73 : 58).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗