Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ESTRADIOL”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28Linked to original sources
PubMed2005

Development and evaluation of a reference measurement procedure for the determination of estradiol-17beta in human serum using isotope-dilution liquid chromatography-tandem mass spectrometry.

Estradiol is the most potent natural estrogen and is derived from the ovaries. Its concentration in blood is measured to determine ovarian function. A reference measurement procedure for estradiol in serum involving isotope-dilution coupled with liquid chromatography-tandem mass spectrometry (LC/MS/MS) has been developed and critically evaluated. A deuterated estradiol (estradiol-d3) was used as an internal standard. The estradiol and its internal standard were extracted from serum matrix using solid-phase extractions and derivatized with dansyl chloride prior to reversed-phase LC/MS/MS. The accuracy of the measurement was evaluated by a comparison of results of this reference method on lyophilized human serum reference materials for estradiol [Certified Reference Materials (CRMs) 576, 577, and 578] with the certified values determined by gas chromatography/mass spectrometry (GC/MS) reference methods and by a recovery study for the added estradiol. The results of this method for estradiol agreed with the certified values within the uncertainty of the measurements for the three CRMs. The recovery of the added estradiol ranged from 100.7 to 101.8%. This method was applied to the determination of estradiol in frozen serum samples from three individual female donors. Excellent reproducibility was obtained with within-set coefficient of variations (CVs) ranging from 0.6 to 2.2% and between-set CVs ranging from 0.2 to 0.4%. Excellent linearity was also obtained, with correlation coefficients of all linear regression lines (measured intensity ratios vs mass ratios) ranging from 0.998 to 1.000. The detection limit at a signal-to-noise ratio of approximately 3 was 0.6 pg of estradiol (or 1 ng/L, as expressed as a concentration). This well-characterized LC/MS/MS method for serum estradiol, which demonstrates good accuracy and precision, low susceptibility to interferences, and comparability with GC/MS reference methods, qualifies as a reference measurement procedure that can be used to provide an accuracy base to which routine methods for estradiol can be compared and that will serve as a standard of higher order for measurement traceability.

Chromatography, Liquid↗
PubMed2002

17beta-estradiol enhances vascular endothelial growth factor production and dihydrotestosterone antagonizes the enhancement via the regulation of adenylate cyclase in differentiated THP-1 cells.

We studied the in vitro effects of sex hormones on vascular endothelial growth factor (VEGF) production in differentiated THP-1 monocytic cells. Phorbol-12-myristate-13-acetate differentiated THP-1 into macrophage-like cells. 17beta-estradiol (10 (-9) M) increased VEGF secretion of controls 3.1-fold in differentiated THP-1 and this effect of 17beta-estradiol was antagonized by dihydrotestosterone, although dihydrotestosterone alone did not alter VEGF secretion. 17beta-estradiol increased steady-state mRNA level of VEGF and the increase was counteracted by dihydrotestosterone in differentiated THP-1, although dihydrotestosterone alone did not alter the VEGF mRNA level. Progesterone did not affect the constitutive and 17beta-estradiol-induced VEGF secretion and mRNA level. Transient transfection revealed that 17beta-estradiol enhanced chloramphenicol acetyl transferase expression driven by VEGF promoter and the enhancement was antagonized by dihydrotestosterone. Adenylate cyclase inhibitor suppressed 17beta-estradiol-induced enhancement of VEGF secretion, mRNA level, and promoter activity, whereas dihydrotestosterone-induced suppression on the effects of 17beta-estradiol was counteracted by 3',5'-adenosine cyclic monophosphate (cAMP) analog. 17beta-estradiol increased intracellular cAMP level by activating adenylate cyclase, while dihydrotestosterone reduced the basal and 17beta-estradiol-increased cAMP level by inhibiting adenylate cyclase. Transfection with 5'-deleted VEGF promoters demonstrated that the region between -88 and -66 bp may be involved in the transcriptional regulation by each hormone. The mutation within activator protein-2 element in this region abrogated the transcriptional stimulation and repression by the respective hormones. 17beta-estradiol activated transcription from activator protein-2-responsive reporter plasmid while dihydrotestosterone antagonized the effect of 17beta-estradiol. These results suggest that 17beta-estradiol enhances VEGF production while dihydrotestosterone antagonizes the effect of 17beta-estradiol via up- or downregulation of adenylate cyclase in differentiated THP-1.

Adenylyl Cyclases↗
PubMed2003

17beta-estradiol inhibits the production of interferon-induced protein of 10 kDa by human keratinocytes.

The natural course of psoriasis is often modulated during pregnancy, indicating the regulatory effect of estrogen or progesterone on psoriasis. Interferon-induced protein of 10 kDa chemoattracts T helper 1 cells, and interferon-induced protein of 10 kDa production by keratinocytes is enhanced in psoriatic skin lesions. We examined in vitro effects of sex hormones on the interferon-induced protein of 10 kDa production by human keratinocytes. 17beta-estradiol inhibited interferon-gamma-induced interferon-induced protein of 10 kDa secretion, mRNA expression, and promoter activity. Interferon-stimulated response element on the promoter was responsible for the inhibition by 17beta-estradiol. Interferon-gamma-induced protein of 10 kDa production was also inhibited by anti-estrogens, ICI 182 780 and tamoxifen, and membrane-impermeable bovine serum albumin-conjugated 17beta-estradiol, suggesting the effects via membrane estrogen receptor, whereas 17alpha-estradiol, progesterone, and dihydrotestosterone had no effects. 17beta-estradiol and bovine serum albumin-conjugated 17beta-estradiol suppressed interferon-gamma-induced transcription through the interferon-stimulated response element and signal transducer and activator of transcription 1alpha binding to interferon-stimulated response element. 17beta-estradiol and bovine serum albumin-conjugated 17beta-estradiol suppressed interferon-gamma-induced tyrosine phosphorylation of signal transducer and activator of transcription 1alpha, and Janus tyrosine kinase 1 and 2. 17beta-estradiol-mediated suppression on the interferon-gamma-induced signal transducer and activator of transcription 1alpha activation and interferon-induced protein of 10 kDa synthesis was counteracted by adenylate cyclase inhibitor SQ22536. 17beta-estradiol, bovine serum albumin-conjugated 17beta-estradiol, ICI 182 780, and tamoxifen increased intracellular 3',5'-adenosine cyclic monophosphate level by activating adenylate cyclase in keratinocytes. Fluorescein isothiocyanate-labeled bovine serum albumin-conjugated 17beta-estradiol bound to the surface of keratinocytes, and mRNA for estrogen receptor beta but not for estrogen receptor alpha was detected in keratinocytes. These results suggest that 17beta-estradiol may interact with the membrane receptor on keratinocytes and generate 3',5'-adenosine cyclic monophosphate by activating adenylate cyclase, which may lead to the inhibition of interferon-gamma-induced signal transducer and activator of transcription 1alpha activation and interferon-induced protein of 10 kDa synthesis.

Binding Sites↗
PubMed1984

17 beta-estradiol for postmenopausal estrogen replacement therapy.

After physiological or surgical menopause, women are suddenly deficient in their main estrogenic hormone, 17 beta-estradiol. Only a very small amount of estradiol is still produced from adrenal precursors. More than 50 per cent of all postmenopausal women suffer for varying periods of time from the symptoms of this estrogen deficiency, most notably vasomotor instability (hot flashes) and sleep disturbances. The trophic symptoms of estrogen deficiency have longer lasting and cumulative consequences: accelerated loss of bone density that eventually increases the risk of fractures, genitourinary atrophy resulting in dyspareunia and urinary atrophy; and lipoprotein changes with increased risk of coronary heart morbidity and mortality. Today estrogen deficiency is mainly treated by oral estrogens--either conjugated equine estrogens or estradiol--in milligram doses far in excess of what would be required by the parenteral route. Taken orally, estradiol is largely transformed to estrone through metabolism in the liver. Certain undesirable side effects of estrogen therapy (e.g., increased renin substrate) are caused by the unphysiologic nature of the oral route of administration. Dosage forms for parenteral estrogen administration have been widely studied: vaginal or percutaneous creams, intranasal solutions, and sublingual tablets. All of these result in a pronounced, transient elevation of plasma concentrations of estradiol and a minor increase of estrone. An improved regimen, which produces more constant plasma concentrations, is achieved with an experimental estradiol implant or with a vaginal ring delivering estradiol. These studies demonstrate that daily estradiol doses of 0.2 mg and less are effective in reducing hot flashes. Effective doses of conjugated estrogens and estradiol administered by different routes achieve estradiol plasma concentrations of similar magnitude (between 35 and 100 pg/ml). Estrone plasma levels vary widely with these different regimens and do not seem to be directly related to efficacy. In summary, the literature indicates that efficacy of estrogen replacement for the treatment of the menopausal symptoms appears to relate to the magnitude of estradiol plasma levels; effective therapy is achieved by an estradiol regimen that maintains plasma estradiol levels of at least 35-55 pg/ml. Efficacy of estrogens in the prevention of osteoporosis as assessed by densitometry has been demonstrated for conjugated oral estrogens.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed2005

Comparative controlled trial of a novel oral estrogen therapy, estradiol acetate, for relief of menopause symptoms.

OBJECTIVE: To compare the efficacy and tolerability of a new oral estradiol prodrug, estradiol acetate, with micronized estradiol or conjugated equine estrogens for alleviation of postmenopausal vasomotor and urogenital symptoms. DESIGN: A total of 249 postmenopausal women experiencing seven or more moderate or severe vasomotor symptoms daily for 1 week or 60 or more symptoms in 1 week were randomized to 0.9 mg of estradiol acetate (n = 79), 1 mg of micronized estradiol (n = 85), or 0.625 mg of conjugated equine estrogens therapy (n = 85). Efficacy endpoints were the change in frequency and severity of vasomotor symptoms from baseline to week 12, participant-assessed urogenital symptoms, and investigator-assessed signs of vaginal atrophy. Efficacy results were considered equivalent if estradiol acetate was at least 80% as effective as estradiol and conjugated estrogens. RESULTS: At week 12, frequency of vasomotor symptoms decreased comparably in all groups, and at weeks 4 and 12, the decrease in frequency of symptoms was statistically equivalent for estradiol acetate and conjugated estrogens. Severity of vasomotor symptoms also improved comparably for all groups, with least squares mean decreases of 1.05 for estradiol acetate, 1.34 for estradiol, and 1.17 for conjugated estrogens at week 12. Urogenital symptoms and vaginal signs showed similar improvement in all groups. Overall, the majority of adverse events were mild or moderate and consistent with estrogen therapy. CONCLUSION: Estradiol acetate 0.9 mg was comparable to 1 mg of estradiol and 0.625 mg of conjugated equine estrogens in reducing the number and severity of vasomotor and urogenital symptoms in postmenopausal women. Oral estradiol acetate was well tolerated.

Adult↗
PubMed1995

17 beta-Estradiol attenuates acetylcholine-induced coronary arterial constriction in women but not men with coronary heart disease.

BACKGROUND: Women are protected from coronary artery disease until the menopause. Ovarian hormones are vasoactive substances that influence both hemodynamic parameters and atheroma formation. Intravenous ethinyl estradiol has been shown to reverse acetylcholine-induced vasoconstriction in cynomolgus monkeys and humans, and 17 beta-estradiol improves exercise-induced myocardial ischemia in female patients. We investigated the effect of the naturally occurring estrogen 17 beta-estradiol on the coronary circulation in postmenopausal women and men with coronary artery disease. METHODS AND RESULTS: We studied nine postmenopausal women 59 +/- 3 years old, mean +/- SEM, and seven men 52 +/- 4 years old with proven coronary artery disease. They underwent measurement of coronary artery diameter and coronary blood flow after intracoronary infusion of acetylcholine 1.6 and 16 micrograms/min before and 20 minutes after intracoronary administration of 2.5 micrograms of 17 beta-estradiol into atherosclerotic, nonstenotic coronary arteries. Changes in coronary artery diameter were measured by quantitative angiography, and changes in coronary blood flow were measured with an intracoronary Doppler catheter. In female patients, acetylcholine 1.6 and 16 micrograms/min caused constriction before the administration of 17 beta-estradiol (-6 +/- 2% and -8 +/- 5%, respectively, compared with baseline). This constrictor response was converted to dilatation after intracoronary administration of 17 beta-estradiol (+8 +/- 2% and +9 +/- 3%, respectively; P < .01 before versus after estrogen). Acetylcholine 1.6 and 16 micrograms/min increased coronary blood flow before and after the infusion of 17 beta-estradiol. However, the mean acetylcholine-induced increases in coronary flow were significantly greater (P < .009) after (126 +/- 37% and 248 +/- 89%, respectively) than before (94 +/- 31% and 143 +/- 49% mL/min, respectively) the administration of 17 beta-estradiol. 17 beta-Estradiol alone had no significant effect on coronary diameter or coronary blood flow (P > .05). Isosorbide dinitrate (1 mg) caused dilatation of the coronary arteries by 11 +/- 2% (P < .005). In men, acetylcholine 1.6 and 16 micrograms/min caused constriction both before and after the administration of 17 beta-estradiol and caused similar increases in coronary blood flow both before and after the intracoronary administration of 17 beta-estradiol. Infusion of intracoronary placebo in six female control patients 55 +/- 3 years old and six male control patients 56 +/- 3 years old did not change coronary diameter responses or coronary blood flow responses to acetylcholine. CONCLUSIONS: 17 beta-Estradiol modulates acetylcholine-induced coronary artery responses of female but not male atherosclerotic coronary arteries in vivo. These human data confirm reports from studies in cynomolgus monkeys that estrogen modulates the responses of atherosclerotic coronary arteries. An enhancement of endothelium-dependent relaxation by natural estrogen (as used in most hormone replacement therapy) may be important in postmenopausal women with established coronary heart disease and may contribute to the acute effect of 17 beta-estradiol on blood flow and its long-term protective effect on the development of coronary artery disease.

Acetylcholine↗
PubMed2004

The 17alpha and 17beta isomers of estradiol both induce rapid spine synapse formation in the CA1 hippocampal subfield of ovariectomized female rats.

Previous studies have demonstrated that estradiol-17beta and estradiol-17alpha both induce short-latency effects on spatial memory in rats, estradiol-17alpha being at least as potent as its 17beta isomer. To determine whether the mechanisms underlying these behavioral responses might include effects on hippocampal synaptic plasticity, CA1 pyramidal spine synapse density (PSSD) was measured in ovariectomized rats within the first few hours after s.c. estrogen injection. PSSD increased markedly (by 24%) 4.5 h after the administration of 45 microg/kg estradiol-17beta. The PSSD response was significantly greater (44% above control) 30 min after estradiol-17beta injection and was markedly dose dependent; a 3-fold lower estradiol-17beta dose (15 microg/kg) did not significantly affect CA1 PSSD at either 30 min or 4.5 h. Estradiol-17alpha was a more potent inducer of PSSD than estradiol-17beta. Dose-response analysis determined an ED50 for the effect of estradiol-17alpha on PSSD of 8.92 +/- 1.99 microg/kg, with a maximal response at 15 microg/kg. These results demonstrate that high doses of estradiol induce rapid changes in CA1 PSSD. CA1 spine synapse formation appears to be more sensitive to estradiol-17alpha than to estradiol-17beta, paralleling previous data on the effects of these two steroids on spatial memory. Rapid remodeling of hippocampal synaptic connections may thus contribute to the enhancement of spatial mnemonic processing observed within the first few hours after estrogen treatment. The potency of estradiol-17alpha suggests that hormone replacement therapy using this steroid might be useful clinically in ameliorating the impact of low endogenous estrogen production on the development and progression of neurodegenerative disorders involving the hippocampus.

Animals↗
PubMed1987

Effects of estradiol on calcium-specific protein phosphorylation in the rat corpus luteum.

Estradiol regulates progesterone synthesis by the corpus luteum of several species. The molecular mechanism(s) of the action of estradiol is unknown, but appears to be independent of exogenous gonadotropins and tissue cAMP. A role for Ca2+ in steroidogenesis has been implicated, and we demonstrate here that estradiol alters Ca-specific protein phosphorylation in rat luteal cells. Corpora lutea obtained from rats hypophysectomized and hysterectomized on day 12 of pregnancy and subsequently treated for 3 days with vehicle or estradiol were assayed in vitro for Ca-specific phosphorylation. Estradiol elevated the content of a number of cytosolic proteins (mol wt X 10(-3), 58, 82, 100, 166, and 183); however, phosphorylation of the 100K protein alone appeared to be specifically enhanced by estradiol. In the presence of Ca2+, phosphorylation of the luteal 100K protein increased 2.33 +/- 0.2-fold in estradiol-treated vs. 1.42 +/- 0.2-fold in vehicle-treated rats (n = 6; P less than 0.05). Phosphorylation of 100K was inhibited by trifluoperazine and stimulated by calmodulin (CaM). Phosphopeptide maps revealed that the 100K luteal protein is identical to the cytosolic CaM-protein kinase III substrate, termed 100K, present in a number of tissues. Estradiol increased both 100K content and CaM-kinase III activity in luteal cells. Immunochemical analysis using antibodies prepared against pancreatic 100K revealed that estradiol treatment increased by at least 5 to 7-fold the luteal content of 100K. In addition, luteal cytosol of estradiol-treated rats enhanced phosphorylation of purified pancreatic 100K 3-fold, whereas that of vehicle-treated rats caused a 1.8-fold stimulation. The effects of estradiol on cytosolic proteins appear to be specific for 100K, since it does not after the activities of CaM-kinases I and II or cAMP-PK. In summary, results of this investigation demonstrate for the first time that estradiol increases the content of several proteins in the corpus luteum; estradiol enhances specifically the Ca-CaM-dependent phosphorylation of a 100K cytosolic protein; and the CaM-kinase III-100K substrate system is hormonally regulated.

Animals↗
PubMed1991

Calcium-calmodulin and calcium-phospholipid dependent phosphorylation of membranous fraction proteins related to the tropic regulation by estradiol in the corpus luteum.

Estradiol assumes a major role in the regulation of growth, vascularization, and progesterone synthesis in the midpregnant rat corpus luteum. To explore whether molecular events triggered by estradiol could be mediated, at least in part, by protein phosphorylation, we investigated whether estradiol treatment in vivo affects endogenous luteal protein phosphorylation systems detectable in vitro. Luteal nuclear, mitochondrial, and microsomal fractions were obtained by differential centrifugation from rats hypophysectomized and hysterectomized on day 12 of pregnancy and treated with or without estradiol for 72 h. Using [gamma-32P]ATP as phosphate donor, proteins were phosphorylated in the presence or absence of either calcium (Ca), Ca plus calmodulin, or Ca plus phospholipid. Phosphoproteins were separated by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and visualized by autoradiography. The Coomassie blue stained proteins and phosphoprotein profiles were markedly different in the various fractions. Estradiol treatment in vivo caused an increase in the basal endogenous phosphorylation of several proteins in vitro. It also substantially enhanced the protein kinase C (PKC) and Ca-calmodulin kinase-dependent phosphorylation of selected proteins in subcellular fractions. The Ca-calmodulin kinase catalyzed phosphorylation of microsomal 56 and 60 kilodalton (kDa) proteins was remarkably increased by estradiol. Proteins (56 and 60 kDa) were also phosphorylated when Ca-calmodulin was added to the nuclear fraction, however, this phosphorylation did not appear to be affected by estradiol treatment. A major PKC substrate in the nuclear fraction was an 80 kDa protein whose phosphorylation was increased remarkably by estradiol treatment. In the mitochondrial fraction the most striking effect of estradiol was a marked increase in PKC-mediated phosphate transfer into a 76 kDa substrate. To determine whether estradiol action on protein phosphorylation was related to its tropic effect in the corpus luteum, the hormone was administered to day 10 hypophysectomized and hysterectomized pregnant rats. In this rat model, where estradiol has no stimulatory effect on either luteal steroidogenesis or growth, neither endogenous nor kinase-mediated phosphorylation was affected by this steroid. In summary, the present investigation has revealed that in vivo treatment with estradiol affects the PKC and the Ca-calmodulin dependent in vitro phosphorylation of selected proteins localized in different subcellular compartments and further suggests that phosphorylation systems are potential control points for estradiol regulation of rat corpus luteum function.

Animals↗
PubMed1998

Regulation of gonadotropin-releasing hormone (GnRH) receptor gene expression in sheep: interaction of GnRH and estradiol.

GnRH and estradiol are important regulators of GnRH receptors. When delivered to the anterior pituitary gland continuously, GnRH decreases numbers of GnRH receptors on gonadotropes. Treatment with estradiol consistently increases numbers of GnRH receptors. Because estradiol acts via intracellular receptors while GnRH exerts its effects through a membrane receptor, it is likely that these hormones influence GnRH receptor expression via different mechanisms. In this experiment, we tested two hypotheses: 1) continuous infusion of GnRH will decrease expression of the GnRH receptor gene; and 2) estradiol will override the negative effects of continuous infusion of GnRH on GnRH receptor expression. Ovariectomized ewes were administered either GnRH (10 microg/h, n = 10) or saline (n = 10) continuously for 136 h. At 124 h, 5 ewes in each group were administered estradiol (25 microg i.m.) and anterior pituitary glands were collected 12 h later. Treatment with GnRH caused an abrupt increase in circulating concentrations of LH, and the maximal mean concentration was observed 4 h after the start of GnRH infusion. Following this increase, concentrations of LH in GnRH-treated ewes declined and were similar to those in saline-treated ewes from 8 h to 124 h. After injection of estradiol at 124 h, circulating concentrations of LH increased in both GnRH- and saline-treated ewes. However, this response occurred within 6 h in ewes treated with GnRH compared with 9 h in ewes treated with saline (P < 0.05). Compared with saline-treated controls, treatment with GnRH decreased mean steady-state amount of GnRH receptor messenger RNA (mRNA) (P < 0.01) and concentration of GnRH receptors (P < 0.05). Treatment with estradiol caused an increase in concentrations of GnRH receptor mRNA (P < 0.05) and GnRH receptors (P < 0.01). Amounts of GnRH receptor mRNA and numbers of GnRH receptors in ewes treated with both GnRH and estradiol were not different from those in the control group but were higher (P < 0.002) relative to ewes treated with GnRH alone. Treatment with GnRH and estradiol also influenced the expression of genes encoding the LHbeta and FSHbeta subunits. Compared with saline-treated controls, treatment with GnRH reduced steady-state amounts of mRNA encoding LHbeta subunit (P < 0.005) and FSHbeta subunit (P < 0.05). Treatment with estradiol caused a decrease in concentrations of FSHbeta subunit mRNA (P < 0.01) but did not affect amounts of LHbeta subunit mRNA. The combined treatment of GnRH and estradiol reduced concentrations of mRNA encoding LHbeta subunit (P < 0.01) and FSHbeta subunit (P < 0.005). From these data we conclude that 1) reduced numbers of GnRH receptors during continuous infusion of GnRH are mediated in part by decreased expression of the GnRH receptor gene; and 2) estradiol is able to override the negative effect of GnRH by stimulating an increase in GnRH receptor gene expression and GnRH receptor concentrations. Therefore, although the gonadotrope becomes refractory to GnRH during homologous desensitization, this desensitization does not affect the cell's ability to respond to estradiol.

Animals↗
PubMed2004

A randomized placebo-controlled trial of short-term graded transdermal estradiol in healthy gonadotropin-releasing hormone agonist-suppressed pre- and postmenopausal women: effects on serum markers of bone turnover, insulin-like growth factor-I, and osteoclastogenic mediators.

The acute effects of estradiol on procollagen type 1 formation in pre- and postmenopausal women are controversial. Twenty-three premenopausal women and 13 postmenopausal women received two consecutive im injections of 3.75 mg leuprolide acetate 3 wk apart to block endogenous ovarian steroidogenesis. Transdermal estradiol therapy commenced on the night of the second leuprolide injection in all subjects, except five pre- and two postmenopausal women who were randomized to receive placebo patches. Estradiol therapy was applied incrementally, with each dose of 0.05, 0.10, 0.15, and 0.20 mg/d administered for 4 consecutive days, to mimic the estradiol changes typifying the follicular phase of the menstrual cycle. Blood aminoterminal propeptide of type I procollagen (PINP), intact osteocalcin (OC), carboxyterminal telopeptide of type I collagen (CTx), IGF-I, and estradiol were measured before and at the end of each estradiol increment. Potential mediators such as osteoprotegerin and receptor activator of nuclear factor-kappaB ligand (RANKL) were also measured. Despite comparable increases in serum estradiol, PINP increased more in postmenopausal compared with premenopausal women (between-group P = 0.03) and occurred at a time when CTx and OC did not change. CTx and IGF-I changed minimally and inconsistently, whereas OC, RANKL, and osteoprotegerin were stable. Repeated measures linear regression disclosed a significant negative association between increases in estradiol and PINP in premenopausal women (P = 0.0006) only. This suggests that lower dose estradiol should greatly increase PINP. Analogous regressions also showed significant negative relationships between changes in estradiol and RANKL in both pre- (P = 0.04) and postmenopausal (P = 0.002) women. Changes in serum markers of bone formation (PINP or OC) did not correlate with those of IGF-I. We conclude that lower dose estradiol rapidly increases osteoblastic collagen synthesis in women at a time when collagen degradation is stable and that this response differs between pre- and postmenopausal women. The effect of estradiol on bone formation does not appear to be mediated by IGF-I. In contrast, RANKL is likely to mediate the effect of estradiol on osteoclastogenesis.

Administration, Cutaneous↗
PubMed2006

In men, peripheral estradiol levels directly reflect the action of estrogens at the hypothalamo-pituitary level to inhibit gonadotropin secretion.

CONTEXT: Estradiol inhibits gonadotropin release in men by an action at the hypothalamus and pituitary. Because of the tissue-specific regulation of aromatase, peripheral estradiol levels may not reflect brain estradiol concentrations. OBJECTIVE: We evaluated whether local aromatization of testosterone in the hypothalamus or pituitary is important for gonadotropin release and to what extent circulating estrogens affect gonadotropin levels and peripheral testosterone levels. DESIGN, SUBJECTS, AND INTERVENTIONS: We suppressed aromatase activity in 10 young healthy men with letrozole 2.5 mg once daily, restored plasma estradiol levels with estradiol patches (100 microg/d for the first week, 50 microg/d the second week, 25 microg/d the third week, and no estradiol patch the fourth week) and measured plasma testosterone, estradiol, LH, FSH, and SHBG levels. RESULTS: The mean estradiol and testosterone levels during the study ranged between 68.6 +/- 38.3 and 12.6 +/- 7.21 pg/ml for estradiol and 179 +/- 91 and 955 +/- 292 ng/dl (mean +/- sd) for testosterone. Levels of testosterone, LH, and FSH were inversely related to peripheral estradiol levels. During letrozole use, the mean plasma estradiol level needed to restore testosterone, LH, and FSH levels to baseline levels was not significantly different from the baseline mean estradiol level. CONCLUSIONS: Local aromatization of testosterone in the hypothalamo-pituitary compartment is not a prerequisite for expression of the inhibitory action of estrogens on gonadotropin secretion in men. Peripheral estradiol levels directly reflect the inhibitory tone exerted by estrogens on gonadotropin release and are a major determinant of peripheral testosterone, LH, and FSH levels.

Adult↗
PubMed2003

N-methyl-D-aspartate receptor activity and estradiol: separate regulation of cell proliferation in the dentate gyrus of adult female meadow vole.

We have previously found that estradiol increases (within 4 h) but then decreases (within 48 h) cell proliferation in the dentate gyrus of adult female ovariectomized (OVX) rats and of intact meadow voles and that estradiol partially stimulates adrenal activity to suppress cell proliferation in rats. Estradiol enhances N-methyl-D-aspartate receptor (NMDAr) activity and NMDAr activation suppresses cell proliferation in the adult rodent dentate gyrus. Therefore, we tested whether estradiol alters cell proliferation in the dentate gyrus of adult OVX female meadow voles by stimulating NMDAr activity. In experiment 1, OVX females were injected with estradiol (10 micro g) or oil and then with NMDA (30 mg/kg) or vehicle 3 h later and bromodeoxyuridine 4 h later (BrdU; 50 mg/kg). Voles were perfused 1 h after BrdU injection. Relative to oil vehicle, estradiol increased (P</=0.001) and NMDA decreased (P</=0.006) labeled cell number. Coadministration of estradiol/NMDA increased labeled cell numbers relative to NMDA alone (P</=0.03), suggesting that within 4 h estradiol does not influence the effect of NMDA receptors on cell proliferation. In experiment 2, OVX females were injected with either estradiol or oil and then with either MK-801 (1 mg/kg) or vehicle 47 h later and BrdU 48 h later. The animals were perfused 1 h after BrdU was injected. Relative to oil-treated voles, estradiol-treated voles had fewer (P<0.006) and MK-801-treated voles had more labeled cells (P</=0.0001) in the dentate gyrus. However, estradiol did not appear to stimulate NMDA receptors to suppress cell proliferation because estradiol (48 h)/MK-801-treated voles had fewer BrdU-labeled cells than oil (48 h)/MK-801-treated voles (P</=0.06). The results show that estradiol time-dependently influences cell proliferation but that estradiol does not stimulate NMDAr activity to influence cell proliferation in the dentate gyrus of adult voles.

Animals↗
PubMed1981

Estrogen and progestogen binding in the myometrium of the ewe. II. Regulation by estradiol and progesterone.

Two experiments were conducted to study the role of estradiol and progesterone in regulating steroid binding sites in sheep uterine myometrium. Exogenous estradiol increased the concentration of estradiol binding sites in nuclei and subsequently increased the total cell content of estradiol binding sites. Estradiol increased the number of progestogen binding sites (promegestone binding) and may have enhanced the translocation of progestogen binding sites to nuclei. Progesterone decreased the number of progestogen binding sites and blocked estradiol-induced increase in cytoplasmic estradiol binding sites. Progesterone did not block the estradiol-induced increase in estradiol binding sites in nuclei. Estradiol increases myometrial RNA to DNA ratios with in 24 hr of a single injection, whereas progesterone did not. Progesterone blocked the estradiol-induced increase in RNA:DNA. Estradiol apparently promotes the synthesis of both types of binding site. Progesterone, on the other hand, appears to inhibit estrogen-induced synthesis of steroid binding sites by blocking estradiol action at the nucleus. Progesterone may also decrease the number of progestogen binding site through a mechanism other than its "anti-estrogenic" action.

Animals↗
PubMed2002

Development and validation of a short-term, serum-free culture system for bovine granulosa cells: evaluation of the effects of somatotropin and growth hormone-releasing factor on estradiol production.

The objective of this study was to develop and validate a short-term, serum-free culture system to determine whether recombinant bovine somatotropin (rbST) or recombinant bovine growth hormone-releasing factor (rbGRF) altered the estradiol-producing capacity of bovine granulosa cells isolated from dominant or subordinate follicles of the first follicular wave. Thus, ovaries were obtained at an abattoir from cows that were between d 2 to 5 or 6 to 10 of the estrous cycle. Three size classes of follicles were isolated from each cow's ovaries: small (2 to 5 mm in diameter), medium (6 to 14 mm), or the largest (6 to 19 mm). In vivo steroid-producing capacity of follicles was assessed by measuring concentration of estradiol, progesterone, androstenedione and 5alpha-dihydrotestosterone in each follicle. In vitro steroid-producing capacity was assessed by culturing granulosa cells from the different follicle sizes for 48 h in serum-free media with 19-OH androstenedione and measuring the estradiol and progesterone concentrations in media at the end of culture. The effect of different doses of FSH, rbST, or rbGRF on estradiol and progesterone production by granulosa cells from each follicle size class during d 2 to 5 or 6 to 10 was also evaluated. A high percentage (91.7%) of the largest follicles obtained on d 2 to 5 was estrogen-active (estradiol > progesterone) compared with other follicle classifications (d 2 to 5, small = 0%, medium = 13.8%; d 6 to 10, small = 0%, medium = 3.3%, largest = 33.3%). Estradiol was highest (P < 0.05) in the largest follicle on d 2 to 5 and correlated positively with follicle diameter. The pattern of in vitro production of estradiol by granulosa cells from the different follicle size classes reflected the original in vivo capacity of follicles to produce estradiol. However, only granulosa cells from the largest estrogen-active follicle on d 2 to 5 produced more estradiol than progesterone in vitro. Progesterone production by granulosa cells from all follicle classifications was increased by FSH, but FSH only enhanced estradiol production by granulosa cells from the largest estrogen-active follicles on d 2 to 5. Recombinant bST blocked the FSH-induced increase in estradiol by granulosa cells from the largest estrogen-active follicles on d 2 to 5, whereas rbGRF had no effect on steroid production. Based on these results, we concluded that short-term, serum-free culture of bovine granulosal cells obtained from first-wave follicles at an abattoir could be used to reflect reliably the original in vivo estradiol-producing capacity of granulosal cells, and that neither rbST nor rbGRF enhance basal or FSH-induced estradiol production by bovine granulosa cells from first-wave follicles.

Androstenedione↗
PubMed2001

Quantitative determination of estradiol fatty acid esters in human pregnancy serum and ovarian follicular fluid.

BACKGROUND: Lipophilic estradiol derivatives carried by lipoprotein particles in blood may mediate antioxidant or endocrine effects. We developed a new quantitative method to determine the concentration of circulating lipophilic estradiol fatty acid esters in human early- and late-pregnancy serum and in ovarian follicular fluid. METHODS: After extraction from serum or follicular fluid, estradiol fatty acid esters were separated from nonesterified estradiol by Sephadex LH-20 column chromatography. The estradiol ester fraction was hydrolyzed by saponification and further purified by several chromatographic steps. The hydrolyzed estradiol esters were measured by time-resolved fluoroimmunoassay. RESULTS: The average estradiol fatty acid ester concentration in serum increased 10-fold during pregnancy, from 40.4 pmol/L (expressed as pmol/L estradiol; range, 25.0-64.2 pmol/L) in early pregnancy (n = 8) to 404 pmol/L (196-731 pmol/L) in late pregnancy (n = 10). The ratio of estradiol ester to nonesterified estradiol remained relatively constant during pregnancy, at 0.4-0.6%. In 10 follicular fluid samples, the mean estradiol ester concentration was 106 nmol/L (56.9-262 nmol/L). Compared with serum, a greater proportion of estradiol in follicular fluid (3.0-10%) was in the esterified form. CONCLUSION: The new method provides a means to measure circulating estradiol fatty acid ester concentrations in human pregnancy serum.

Esters↗
PubMed1991

Improvement of estradiol 17 beta-D-glucuronide cholestasis by intravenous administration of dimethylethanolamine in the rat.

The intravenous administration of dimethylethanolamine in the rat promotes a selective enrichment of liver membranes with polyunsaturated phosphatidylcholines. The effect of dimethylethanolamine pretreatment on cholestasis induced by estradiol 17 beta-D-glucuronide, a potent cholestatic agent, was assessed in this study. Dimethylethanolamine, dissolved in sodium-taurocholate was infused intravenously (0.3 mg/kg/min) for 15 hr. One group of control rats (estradiol 17 beta-D-glucuronide controls) received the bile salt only. An estradiol 17 beta-D-glucuronide bolus was then injected intravenously (10.4 mg/kg) into dimethylethanolamine-pretreated and estradiol 17 beta-D-control rats, and its effect on bile flow and biliary lipid secretion was compared for 3 hr. The estradiol 17 beta-D-glucuronide inhibitory effect on bile flow and biliary lipid secretion was significantly antagonized by dimethylethanolamine pretreatment. The maximum inhibition of bile flow was found 30 min after estradiol 17 beta-D-glucuronide administration, when it decreased from 3.5 +/- 0.4 microliters/min/100 gm (basal) to 0.9 +/- 0.3 microliters/min/100 gm in estradiol 17 beta-D-glucuronide controls, whereas in dimethylethanolamine-pretreated rats this decreased only from 3.2 +/- 0.4 (basal) to 2.3 +/- 0.4 microliters/min/100 gm. Bile flow and the biliary secretion of cholesterol, phosphatidylcholine and bile salts were significantly higher in the dimethylethanolamine-pretreated rats than in estradiol 17 beta-D-glucuronide controls (p less than 0.02) during the cholestatic phase. The inhibitory effect of estradiol 17 beta-D-glucuronide on bile flow was associated with a marked decrease of membrane fluidity (p less than 0.001) assessed by 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy and with a cholesterol enrichment of microsomes, sinusoidal and canalicular liver plasma membranes and inhibition of sinusoidal Na+,K(+)-ATPase activity (p less than 0.05). These membrane alterations persisted 180 min after estradiol 17 beta-D-glucuronide administration despite complete normalization of bile flow. Dimethylethanolamine pretreatment significantly counteracted the reduction of membrane fluidity (p less than 0.001), the cholesterol enrichment and the inhibition of Na+,K(+)-ATPase (p less than 0.05) promoted by estradiol 17 beta-D-glucuronide administration in all membrane subfractions 30 and 180 min after administration. In addition, dimethylethanolamine-pretreated rats had more polyunsaturated fatty acids in membrane phosphatidylcholine with respect to the control groups. Dilatation of canaliculi and loss of microvilli were evident in estradiol 17 beta-D-glucuronide controls 180 min after estradiol 17 beta-D-glucuronide administration.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1982

Estrone receptor formation during the processing of estradiol-receptor complex in MCF-7 cells.

Human breast cancer cells (MCF-7, maintained in long-term culture) contain separate estrogen receptors specific for either 17 beta-estradiol or estrone. Utilizing optimum conditions for the protamine sulfate assay, it has been possible to demonstrate both receptors in the 0.6 M KCl extract of nuclei and in the cytosol. Similarly, in the exchange assay, high-affinity low-capacity binding sites for 17 beta-estradiol and estrone have been found in the salt-extracted nuclear residue. Dissociation constants and binding capacities were determined for either receptor in the absence of the other [e.g., estrone receptor (E1R) in the cytosol or nuclear residue from 17 beta-estradiol-stimulated cells] or, when both receptors were present, a saturating amount of the other estrogen (unlabeled) was added to the assay mixture (e.g., the salt-extractable nuclear receptors). Specificity was demonstrated by the inability of estrone to compete with 17 beta-[2,4,6,7-3H]estradiol for the 17 beta-estradiol receptor (E2R) at molar excesses less than 10-fold. Likewise, there was no inhibition of [6,7-3H]estrone binding to its receptor by molar excesses of 17 beta-estradiol below 100-fold. Other steroid hormones were very weak competitors of [6,7-3H]estrone, even at 1000-fold molar excesses. The quantitative relationships of these two estrogen receptors were shown to fluctuate in the various cellular compartments following incubation (37 degrees) of MCF-7 cells with 10(-8) M 17 beta-estradiol. This level of 17 beta-estradiol elicited the translocation of all detectable cytosolic E2R to the nucleus, where, after an incubation of 1 hr, the salt-resistant 17 beta-estradiol disappeared and 40% of the extractable 17 beta-estradiol-binding capacity was lost (processed). Simultaneously, the E1R which remained in the nuclear residue appeared in the nuclear extract, and ultimately this receptor accumulated in the cytosol. The estrone-binding capacity (0.78 pmol/mg DNA) which appeared following the processing of E2R nearly equalled the loss of 17 beta-estradiol binding sites per cell (0.85 pmol/mg DNA). Concentrations of 17 beta-estradiol which elicited the greatest processing of E2R in these incubations brought about the appearance of maximum levels of E1R in MCF-7 cells. Considering these results in the light of data previously reported from this laboratory concerning the metabolic and ligand fate of 17 beta-[3H]estradiol in MCF-7 cells, processing would appear to involve the formation of E1R in the salt-resistant nuclear compartment followed by the accumulation of E1R in the cytosol.

Binding, Competitive↗