Biol Reprod. 2002 Sep;67(3):829-36.
Influence of estradiol on NADPH diaphorase/neuronal nitric oxide synthase activity and colocalization with progesterone or type II glucocorticoid receptors in ovine hypothalamus.

Dufourny L, Skinner DC.

Department of Clinical Veterinary Science, University of Bristol, Langford BS40 5DU, United Kingdom. dufournwyo.edu

Nitric oxide (NO) has been shown to play an important role in both the neuroendocrine reproductive and stress axes, which are closely linked. Because progesterone (P4) receptors (PRs) and glucocorticoid receptors (GRs) are not found in GnRH neurons and the NOergic system has been implicated in the control of GnRH secretion, this study aimed to ascertain whether steroids altered the NOergic system. Our first objective was to map the distribution of NO synthase (NOS) cells in the ovine preoptic area (POA) and hypothalamus and to determine whether NOS activity is enhanced by estradiol (E2) treatment. Using NADPH diaphorase (NADPHd) histochemistry, we found that NADPHd-positive neurons were spread throughout the ovine POA and hypothalamus, and that all NADPHd cells were immunoreactive for NOS. In response to estradiol, a significant increase in the number of NADPHd cells was noted only in the ventrolateral region of the ventromedial nucleus (VMNvl), with no significant difference in the POA or arcuate nucleus. Progesterone and glucocorticoid receptors were colocalized with NADPHd reactive neurons in the POA, arcuate nucleus, and VMNvl of ewes in both treatment groups. In ewes receiving estradiol, the number of NADPHd-positive cells containing steroid receptors in the POA (PR, 81%; GR, 79%) and arcuate nucleus (PR, 89%; GR, 84%) was similar, but in the VMNvl, fewer NADPHd-positive cells contained GR (PR, 88%, GR, 31%). These data show that estradiol up-regulates NOS activity in a site-specific manner and that the influence and possible interaction of progesterone and corticosteroids on NO producing cells may differ according to the neural l




Am J Obstet Gynecol. 2002 Aug;187(2):375-81.
17 beta-Estradiol induces a rapid, endothelium-dependent, sex-specific vasodilatation in spontaneous constricted rat arterioles.

Smolders RG, van der Mooren MJ, Kenemans P, van der Linden PW, Stehouwer CD, Sipkema P.

Project Aging Women, and the Institute for Cardiovascular Research-Vrije Universiteit, Department of Obstetrics and Gynecology, VU University Medical Center, Amsterdam, The Netherlands.

OBJECTIVE: Our purpose was to resolve the apparent contradiction between the endothelium-dependent and endothelium-independent vasodilator effects of 17 beta-estradiol reported in different studies. STUDY DESIGN: The inner diameters of isolated pressurized spontaneously constricted muscle arterioles (diameter = 63 microm) from Wistar rats (n = 21) were measured during exposure to 17 beta-estradiol, and the role of the endothelium and the influence of sex were assessed. RESULTS: A dose-dependent dilatation was observed during exposure to 17 beta-estradiol concentrations from 10(-10) to 10(-4) mol/L. Arterioles of female rats displayed significantly more dilatation than vessels from male rats. The dilatation was significantly less in endothelium-denuded arterioles or after pretreatment with and in the presence of a nitric oxide synthase inhibitor. CONCLUSIONS: These results provide strong evidence that, in addition to an endothelium-independent effect, 17 beta-estradiol has a dose-dependent, endothelium-mediated, rapid vasodilatory effect on muscle arterioles from the rat, which is stronger in female rats than in male rats.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12193928&dopt=Abstract estradiol




J Endocrinol. 2003 Mar;176(3):367-79.
Dose- and time-dependent effects of 17beta-oestradiol on insulin sensitivity in insulin-dependent tissues of rat: implications of IRS-1.

Gonzalez C, Alonso A, Diaz F, Patterson AM.

Departamento de Biologia Funcional (Fisiologia), Facultad de Medicina, Universidad de Oviedo, C/Julian Claveria s/n 33006 Oviedo, Spain. tinoorreo.uniovi.es

Numerous studies have suggested that ovarian hormones are able to modulate insulin sensitivity, but their exact role remains unclear. We have investigated whether different doses of 17beta-oestradiol mediate changes in insulin sensitivity and if these changes could be related to modifications of insulin receptor substrate-1 (IRS-1). Female rats were ovariectomized and later separated into three groups: untreated; treated with a dose of 17beta-oestradiol sufficient to reproduce gestational plasma concentrations of 17beta-oestradiol (group E); and treated with a dose 100 times greater than that given to group E (group E2). A euglycaemic-hyperinsulinaemic clamp was used to measure insulin sensitivity. Changes in IRS-1 were analysed by Western blotting and RT-PCR assays. In group E we found a decrease in insulin sensitivity between days 11 and 16 of treatment as in late gestation, whereas in the untreated group and group E2, development of insulin resistance was observed throughout the treatment. In contrast, whereas in group E2 insulin resistance throughout the hormonal treatment was related to diminished expression and phosphorylation of IRS-1, in group E the decrease in insulin sensitivity between days 11 and 16 of treatment was not related to a decrease in IRS-1 expression. Our results suggest that the effects of oestradiol on insulin sensitivity were dose-dependent and that the insulin resistance associated with a high dose of 17beta-oestradiol was related to downregulation of IRS-1 expression.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12630922&dopt=Abstract estradiol




Aquat Toxicol. 2002 Oct 2;60(1-2):101-10.
A comparison of the estrogenic potencies of estradiol, ethynylestradiol, diethylstilbestrol, nonylphenol and methoxychlor in vivo and in vitro.

Folmar LC, Hemmer MJ, Denslow ND, Kroll K, Chen J, Cheek A, Richman H, Meredith H, Grau EG.

US Environmental Protection Agency, 1 Sabine Island Drive, Gulf Breeze, FL 32561, USA. folmar.leropamail.epa.gov

Five natural, pharmaceutical, or xenobiotic chemicals [17beta-estradiol (E2), ethynylestradiol (EE2), diethystilbestrol (DES), methoxychlor (MXC), nonylphenol (NP)] were tested in two in vitro assays [yeast estrogen screen (YES), MCF-7 breast tumor cell proliferation (E-Screen)], and compared with previously reported results from two in vivo male sheepshead minnow vitellogenin (VTG) production studies. The purpose of this investigation was to determine how accurately the two in vitro assays predicted responses observed in live animals. EC50 values for all five chemicals were approximately one order of magnitude less sensitive in the YES assay than in the MCF-7 assay. Based on the EC50 values, DES was 1.1 (YES) to 2.5 (MCF-7) times more potent in these receptor binding assays than was E2, while EE2 was slightly less potent than E2 in the YES assay (0.7) and nearly twice as potent (1.9) as E2 in the MCF-7 assay. EE2 and DES were of approximately equal potency in the 13-day sheepshead minnow VTG production bioassay. Both MXC and NP were 10(7) times less potent than E2 in the YES assay, MXC was 10(5) times less estrogenic than E2 in the MCF-7 assay, while both were approximately 100 times less potent than E2 in the live animal bioassay. The in vitro tests were substantially less sensitive (at least 1000 times) than the sheepshead minnow VTG assay for estimating estrogenic potency of the two xenobiotic chemicals, which suggests that in vitro-based, large-scale screening programs could potentially result in many false negative evaluations.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12204590&dopt=Abstract estradiol


Clin Endocrinol (Oxf). 2001 Nov;55(5):649-57.
The CAG repeat polymorphism in the androgen receptor gene affects bone density and bone metabolism in healthy males.

Zitzmann M, Brune M, Kornmann B, Gromoll J, Junker R, Nieschlag E.

Institute of Reproductive Medicine of the University, Munster, Germany.

OBJECTIVE: Bone metabolism and bone density (BD) are influenced by sex hormones. Testosterone (T) action is exerted through the androgen receptor (AR). We investigated the potential impact of the CAG repeat (CAGR) polymorphism within the AR gene on BD and bone metabolism in healthy younger males. PATIENTS AND MEASUREMENTS: The number of CAGRs in 110 healthy men aged 20-50 years was determined by sequence analysis. We assessed BD by the radiation-free method of quantitative ultrasound (QUS) of the phalanges. Serum levels of bone-specific alkaline phosphatase (BAP) and urine secretion of free deoxypyridinoline (DPD, corrected for creatinine), serum levels of sex hormones, body fat content and lifestyle factors were determined. RESULTS: In stepwise multiple regression models controlling for age, body fat content and lifestyle factors, the number of CAGRs was an independent negative predictor of BD (partial r = - 0.286, P = 0.001), whereas it was positively associated with markers of bone turnover (for BAP: partial r = 0.32, P= 0.001; for DPD: partial r = 0-241, P = 0.013). Levels of free T and oestradiol showed an independent and positive association with BD; age contributed significantly to lower BD. Age and free T were negatively associated with markers of bone turnover, whereas oestradiol showed a positive correlation with BAP and DPD. ANOVA in groups according to age and the CAGR length suggested an increased age-dependent bone loss in subjects with a CAGR length of 22-31 compared with 14-21 CAGRs (overall P < 0.01). CONCLUSIONS :A high number of CAG repeats within the androgen receptor gene attenuates testosterone effects on bone density and bone metabolism. This seems to be associated with acce




Clin Endocrinol (Oxf). 2001 Dec;55(6):789-95.
An ultrasensitive assay revealed age-related changes in serum oestradiol at low concentrations in both sexes from infancy to puberty.

Ikegami S, Moriwake T, Tanaka H, Inoue M, Kubo T, Suzuki S, Kanzakili S, Seino Y.

Department of Paediatrics, Okayama University Medical School, Japan.

OBJECTIVE: Intensive studies of oestrogen receptors have suggested extragonadal functions of oestrogen. However, the in vivo extragonadal functions of oestradiol remain unclear because of the lack of an adequate assay system at low concentrations. In this study, we assessed the usefulness of a new ultra-sensitive assay for children. METHODS: Serum oestradiol was measured with an ultrasensitive assay (assayable concentration: 5-1,835 pmol/l: ESTR-US-CT, CIS biointernational, France). Intra- and interassay coefficients of variation at low concentrations (< 36.7 pmol/l) were 8.2 +/- 6.8 (0.1-31.2)% and 8.3 +/- 3.7 (7.5-12.9)%, respectively. SUBJECTS: Sera from 88 healthy children (55 males and 33 females; 1 month to 16 years old) and 31 patients who underwent gonadal suppression therapy were analysed. RESULTS: Age-related changes were observed in both sexes. Serum oestradiol concentrations in childhood decreased slightly compared to those in infancy, then increased at puberty. Most prepubertal children showed oestradiol concentrations lower than 36.7 pmol/l. A study on patients who underwent gonadal suppression therapy revealed oestradiol changes within low concentrations, depending on the stage of the therapy. CONCLUSIONS: The new assay was considered precise enough for the assessment of oestradiol secretion at low concentrations in childhood. Age-related changes in serum oestradiol suggested gonadal activity in the prepubertal period. This assay could be a powerful tool for investigating novel oestradiol functions in vivo.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11895221&dopt=Abstract estradiol




Pharmacology. 2002 May;65(1):26-31.
Effect of 17beta-estradiol exposure on vasorelaxation induced by K(+) channel openers and Ca(2+) channel blockers.

Tsang SY, Yao X, Chan HY, Chen ZY, Ming WC, Huang Y.

Department of Physiology, Chinese University of Hong Kong, Shatin, Hong Kong, PR China.

17beta-Estradiol has been shown to relax blood vessels partly through inhibition of Ca(2+) channels at supraphysiological concentrations; however, it is unknown whether acute exposure of the isolated artery rings to near physiological concentrations of sex steroid hormones could modulate the ionic channels that are involved in regulation of vascular tone. Brief incubation (20 min) with 17beta-estradiol (1-3 nmol/l) did not alter the relaxant response to three blocking agents of L-type voltage-sensitive Ca(2+) channels, nifedipine, diltiazem and verapamil in either endothelium-intact or endothelium-denuded rat mesenteric artery rings. In contrast, 17beta-estradiol at 3 nmol/l significantly attenuated the relaxation induced by K(+) channel openers, cromakalim and pinacidil in endothelium-denuded rings. Similarly, preincubation with progesterone (3 nmol/l) inhibited pinacidil-induced relaxation with much less effect on cromakalim-induced relaxation. It appears that 17beta-estradiol and progesterone attenuated the cromakalim- and pinacidil-induced relaxation in a different manner. These results suggest that acute exposure to female sex steroid hormones at near physiological levels may reduce the activity of ATP-sensitive K(+) channels in the rat arteries. Copyright 2002 S. Karger AG, Basel

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11901298&dopt=Abstract estradiol




J Neurochem. 2002 Jan;80(2):307-16.
Evaluation of the protective effect of oestradiol against toxicity induced by 6-hydroxydopamine and 1-methyl-4-phenylpyridinium ion (Mpp+) towards dopaminergic mesencephalic neurones in primary culture.

Callier S, Le Saux M, Lhiaubet AM, Di Paolo T, Rostene W, Pelaprat D.

Unite 339 INSERM, Hopital Saint Antoine, Paris, France.

Recent findings suggest that gonadal steroid hormones are neuroprotective and may provide clinical benefits in delaying the development of Parkinson's disease. In this report we investigated the ability of oestradiol to protect mesencephalic dopaminergic neurones cultured in serum-free or serum-supplemented medium from toxicity induced by 6-hydroxydopamine or 1-methyl-4-phenylpyridinium ion (MPP+). The efficiency of both toxins and oestradiol was evaluated by tyrosine hydroxylase (TH) immunocytochemistry, [3H]dopamine ([3H]DA) uptake, length of dopaminergic processes and lactate dehydrogenase (LDH) release measurement. In cultures grown in serum-supplemented medium, a 2-h pre-treatment with high concentrations (10-100 microM) of 17beta-oestradiol or 17alpha-oestradiol, the stereoisomer with weak oestrogenic activity, protected both dopaminergic and non-dopaminergic neurones from toxicity induced by 6-hydroxydopamine (6-OHDA; 40 or 100 microM) and by the high MPP+ concentrations (50 microM) necessary to obtain significant neuronal death under those culture conditions. At these concentrations, MPP+ was no longer selective for dopaminergic neurones but affected all cells present in the culture. In contrast, the hormonal treatments did not protect against selective degeneration of dopaminergic neurones induced by lower MPP+ concentrations (below 10 microM), related to inhibition of complex I of respiratory chain. In cultures grown in serum-free medium, oestradiol concentrations higher than 1 microM induced neuronal degeneration and no protection against 6-OHDA or MPP+ toxicity was observed at lower concentrations of the steroid. The




Proc Natl Acad Sci U S A. 2002 Mar 19;99(6):4055-60.
Testosterone attenuates expression of vascular cell adhesion molecule-1 by conversion to estradiol by aromatase in endothelial cells: implications in atherosclerosis.

Mukherjee TK, Dinh H, Chaudhuri G, Nathan L.

Department of Obstetrics and Gynecology, University of California Los Angeles School of Medicine, Los Angeles, CA 90095-1740, USA.

We previously reported that testosterone attenuated atherogenesis in LDLR(-/-) male mice, and that this effect of testosterone was most likely caused by its conversion to estradiol. Estradiol inhibits vascular cell adhesion molecule-1 (VCAM-1) expression, and expression of VCAM-1 is one of the early events in atherogenesis. We assessed the cellular mechanism(s) involved by which testosterone attenuates atherogenesis. We evaluated whether testosterone inhibited TNFalpha-induced VCAM-1 expression via its conversion to estradiol by the enzyme aromatase in human umbilical vein endothelial cells (HUVEC). Aromatase mRNA was dedected by reverse transcription-PCR in these cells. Testosterone (30 nM-1 microM) attenuated VCAM-1 mRNA expression in a concentration-dependent manner. The non aromatizable androgen, dihydrotestosterone, had no effect on VCAM-1 mRNA expression. Testosterone was less effective in attenuating VCAM-1 expression in the presence of anastrozole, an inhibitor of aromatase, indicating that testosterone inhibited VCAM-1 via conversion to estradiol. Estradiol also attenuated VCAM-1 mRNA expression, but this action was not abolished in the presence of anastrozole, indicating that anastrozole itself did not modulate VCAM-1 mRNA expression. The effect of testosterone on VCAM-1 mRNA expression was inhibited in the presence of the estrogen receptor antagonist, ICI-182780. Testosterone also attenuated TNFalpha-induced VCAM-1 protein expression, and this attenuation was abolished in the presence of anastrozole. In conclusion, testosterone inhibited VCAM-1 mRNA and protein expression in HUVEC by its conversion to es



Indian J Exp Biol. 2001 Nov;39(11):1096-102.
Effect of estradiol-17beta on cell area, lumen area and trehalase activity of posterior silk gland of Bombyx mori L.

Keshan B, Ray AK.

Department of Animal Physiology, Bose Institute, Calcutta, India. bkeshaotmail.com

Estradiol-17beta (E2) at the dose of 1 microg/g caused an increase in cell area, lumen area and the total (cell + lumen) area of posterior silk gland (PSG) in Bombyx mori indicating that exogenously applied estradiol-17beta has a regulatory influence on silk gland activity. A dose-dependent variation in trehalase activity of PSG was found on the 5th day after topical administration of estradiol on 1st and 2nd day of the fifth larval instar. Of all the doses of E2 used, 1 microg/g dose had maximum stimulatory effect on trehalase activity. Co-administration of each of a specific receptor antagonist for estradiol, the ICI-182780 and a protein biosynthetic blocker, cycloheximide with E2 suppressed the E2-induced increase in silk gland activity. The results suggest some specific metabolic action of E2 on silk gland and offer a promising way for future investigations regarding the physiological significance of vertebrate steroids in insects.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11906100&dopt=Abstract estradiol