Estrogen replacement therapy and cardioprotection: mechanisms and controversies

Epidemiological and case-controlled studies suggest that estrogen replacement therapy might be beneficial in terms of primary prevention of coronary heart disease (CHD). This beneficial effect of estrogens was initially considered to be due to the reduction of low density lipoproteins (LDL) and to increases in high density lipoproteins (HDL). Recent studies have shown that estrogens protect against oxidative stress and decrease LDL oxidation. Estrogens have direct effects on the arterial tissue and modulate vascular reactivity through nitric oxide and prostaglandin synthesis. While many of the effects of estrogen on vascular tissue are believed to be mediated by estrogen receptors alpha and ß, there is evidence for `immediate non-genomic' effects. The role of HDL in interacting with 17ß-estradiol including its esterification and transfer of esterified estrogens to LDL is beginning to be elucidated. Despite the suggested positive effects of estrogens, two recent placebo-controlled clinical trials in women with CHD did not detect any beneficial effects on overall coronary events with estrogen therapy. In fact, there was an increase in CHD events in some women. Mutations in thrombogenic genes (factor V Leiden, prothrombin mutation, etc.) in a subset of women may play a role in this unexpected finding. Thus, the cardioprotective effect of estrogens appears to be more complicated than originally thought and requires more research.

Effects of estrogen on the vascular system

The cardiovascular protective actions of estrogen are partially mediated by a direct effect on the vessel wall. Estrogen is active both on vascular smooth muscle and endothelial cells where functionally competent estrogen receptors have been identified. Estrogen administration promotes vasodilation in humans and in experimental animals, in part by stimulating prostacyclin and nitric oxide synthesis, as well as by decreasing the production of vasoconstrictor agents such as cyclooxygenase-derived products, reactive oxygen species, angiotensin II, and endothelin-1. In vitro, estrogen exerts a direct inhibitory effect on smooth muscle by activating potassium efflux and by inhibiting calcium influx. In addition, estrogen inhibits vascular smooth muscle cell proliferation. In vivo, 17ß-estradiol prevents neointimal thickening after balloon injury and also ameliorates the lesions occurring in atherosclerotic conditions. As is the case for other steroids, the effect of estrogen on the vessel wall has a rapid non-genomic component involving membrane phenomena, such as alteration of membrane ionic permeability and activation of membrane-bound enzymes, as well as the classical genomic effect involving estrogen receptor activation and gene expression.

Estrogen enhances vasoconstrictive remodeling after injury in male rabbits

The complete spectrum of estrogen vascular effects remains unclear. In particular, estrogen effects in the vascular response to profound injury in males have not been explored in detail. Therefore, we submitted 44 male New Zealand rabbits weighing 3.4 ± 0.6 kg to overdistention balloon injury of the right iliac artery. Rabbits were given 17ß-estradiol (5.45 µmol/day, sc) or vehicle for 7 days before and 14 days after injury, when the arteries were examined by post-mortem histomorphometry. Arteriographic caliber was assessed in vivo at baseline and before sacrifice. On day 14 after injury, in vivo arteriographic caliber (baseline = 2.44 ± 0.43 mm) was decreased by 23.1 ± 0.1% in controls and by 44.5 ± 0.1% in estrogen-treated rabbits (P < 0.001). Neither the neointimal area nor the neointima/media area ratio changed after estrogen treatment. Collagen fraction was increased in the media and neointima of estrogen-treated rabbits vs control (1.38 ± 1.30 vs 0.35 ± 0.67, respectively, P = 0.01). Taken together, these findings suggest that estrogen increased negative vascular remodeling. Transcription of endothelial and inducible nitric oxide synthases (eNOS and iNOS) was analyzed by RT-PCR. eNOS mRNA expression was marginally increased after estrogen (P = 0.07) and injury. iNOS mRNA was increased 2- to 3-fold on day 14 after injury. With estrogen treatment, iNOS mRNA increased in uninjured arteries and exhibited a further 5.5-fold increase after injury. We concluded that estrogen increased lumen loss after balloon injury in male rabbits, likely by increased negative remodeling, which may be related to increased iNOS transcriptional rates.

Études du remodelage vasculaire utérin durant la grossesse : caractérisation du rôle de l’œstrogène et de son action vasorelaxante

La grossesse est un état physiologique particulier où de nombreux changements fonctionnels et structuraux surviennent. Chez la rate, pour répondre aux besoins grandissants du fœtus, l’artère utérine se développe pour atteindre le double de son diamètre original avant parturition. Par conséquent, le débit sanguin utérin augmente d’environ vingt fois. Pour ce faire, les vaisseaux utérins sont l’objet d’un remodelage caractérisé par une hypertrophie et une hyperplasie des différentes composantes de la paroi. De plus, ce remodelage est complètement réversible après la parturition, par opposition au remodelage vasculaire « pathologique » qui affecte les artères systémiques, dans l’hypertension chronique, par exemple. La grossesse s’accompagne aussi de modifications hormonales importantes, comme les œstrogènes dont la concentration s’accroît progressivement au cours de cette période. Elle atteindra une concentration trois cents fois plus élevée avant terme que chez une femme non gravide. Cette hormone possède de multiples fonctions, ainsi qu’un mode d’action à la fois génomique et non génomique. Considérant l’ensemble de ces éléments, nous avons formulé l’hypothèse que l’œstradiol serait responsable de modifier la circulation utérine durant la grossesse, par son action vasorelaxante, mais aussi en influençant le remodelage de la vasculature utérine. Nous avons montré que le 17β-Estradiol (17β-E2) produit une relaxation due à un effet non génomique des artères utérines en agissant directement sur le muscle lisse par un mécanisme indépendant du monoxyde d’azote et des récepteurs classiques aux œstrogènes (ERα, ERβ). De plus, la relaxation induite par le 17β-E2 dans l’artère utérine durant la gestation est réduite par rapport à celle des artères des rates non gestantes. Ceci serait attribuable à une diminution de monoxyde d’azote provenant de la synthase de NO neuronale dans les muscles lisses des artères utérines. Nos résultats démontrent que le récepteur à l’œstrogène couplé aux protéines G (GPER), la protéine kinase A (PKA) et la protéine kinase G (PKG) ne sont pas impliqués dans la signalisation intracellulaire associée à l’effet vasorelaxant induit par le 17β-E2. Cependant, nous avons montré une implication probable des canaux potassiques sensibles au voltage, ainsi qu’un rôle possible des canaux potassiques de grande conductance activés par le potentiel et le calcium (BKCa). En effet, le penitrem A, un antagoniste présumé des canaux potassiques à grande conductance, réduit la réponse vasoralaxante du 17β-E2. Toutefois, une autre action du penitrem A n’est pas exclue, car l’ibériotoxine, reconnue pour inhiber les mêmes canaux, n’a pas d’effet sur cette relaxation. Quoi qu’il en soit, d’autres études sont nécessaires pour obtenir une meilleure compréhension des mécanismes impliqués dans la relaxation non génomique sur le muscle lisse des artères utérines. Quant à l’implication de l’œstrogène sur le remodelage des artères utérines durant la gestation, nous avons tenté d’inhiber la synthèse d’œstrogènes durant la gestation en utilisant un inhibiteur de l’aromatase. Plusieurs paramètres ont été évalués (paramètres sanguins, réactivité vasculaire, pression artérielle) sans changements significatifs entre le groupe contrôle et celui traité avec l’inhibiteur. Le même constat a été fait pour le dosage plasmatique de l’œstradiol, ce qui suggère l’inefficacité du blocage de l’aromatase dans ces expériences. Ainsi, notre protocole expérimental n’a pas réussi à inhiber la synthèse d’œstrogène durant la grossesse chez le rat et, ce faisant, nous n’avons pas pu vérifier notre hypothèse. En conclusion, nous avons démontré que le 17β-E2 agit de façon non génomique sur les muscles lisses des artères utérines qui implique une action sur les canaux potassiques de la membrane cellulaire. Toutefois, notre protocole expérimental n’a pas été en mesure d’évaluer les effets génomiques associés au remodelage vasculaire utérin durant la gestation et d’autres études devront être effectuées.

Dégradation chimique et biologique de neuf contaminants émergents dans les eaux de surfaces et les effluents primaires d’eaux usées municipales

Un protocole inspiré du test de simulation 309 de l’Organisation de coopération et de développement économiques (OCDE) nous a permis de mesurer la dégradation chimique (excluant la photolyse) dans des eaux de surface de même que la dégradation chimique et biologique de neuf contaminants émergents dans l’effluent d’un décanteur primaire d’eau usée municipale. Les données étaient compatibles avec le modèle de cinétique de pseudo ordre un. Les résultats démontrant une persistance de plus d’un an dans les eaux de surface et de 71 jours dans l’effluent du décanteur primaire suggèrent que les dégradations chimique et biologique ne contribuent pas significativement à la diminution de: atrazine, déséthylatrazine, carbamazépine et diclofénac dans la phase aqueuse des systèmes testés. Les autres composés se sont dégradés à différents niveaux. Le 17ß-estradiol ainsi que l’éthinylestradiol, la noréthindrone, la caféine et le sulfaméthoxazole ont tous été sujet à la dégradation biologique dans les effluents du décanteur primaire d’eau usée avec des constantes de dégradation k et des demi-vies t1/2 mesurées allant respectivement de 0.0082 à 0.59 j-1 et de 1.2 à 85 jours. Les paramètres de cinétique mesurés peuvent être combinés aux concentrations typiques des composés à l’étude dans un décanteur primaire d’eau usée pour y calculer leur vitesse de dégradation. Cependant, puisque les décanteurs primaires dans les usines de traitement d’eaux usées ont généralement des temps de résidence de quelques heures seulement, il est improbable que les neufs contaminants émergents à l’étude diminuent significativement par ces processus durant leur passage dans le compartiment.

Estrógeno e pré-condicionamento : efeitos neuroprotetores e possíveis mecanismos de ação em modelos in vitro e in vivo de isquemia cerebral

As bases moleculares da neuroproteção contra a isquemia mediada por estrógeno continuam obscuras, assim como os mecanismos envolvendo a tolerância ao dano isquêmico subseqüente induzida por pré-condicionamento. Neste trabalho foi estudado se as vias de sinalização celular da PI3-K (fosfatidil inositol 3-quinase) e da MEK/ERK 1/2 estariam envolvidas na neuroproteção induzida por estrógeno, bem como alguns parâmetros de estresse oxidativo, especificamente o conteúdo de radicais livres, um índice de dano oxidativo a proteínas e a capacidade antioxidante total. Também foi estudado o possível envolvimento dos transportadores de glutamato (EAAT1 e EAAT2) e dos receptores de estrógeno (ERα e ERβ) nos efeitos neuroprotetores do estrógeno e do pré-condicionamento. Para este fim, foram utilizados os modelos in vitro de culturas organotípicas de fatias hipocampais e fatias hipocampais preparadas a fresco expostas à privação de oxigênio e glicose (POG) e o modelo in vivo de hipóxia-isquemia neonatal. Em culturas tratadas tanto aguda como cronicamente com 17β-estradiol, a morte celular induzida por POG foi diminuída acentuadamente quando comparada com as culturas tratadas apenas com veículo. Este efeito neuroprotetor foi evitado por LY294002 (inibidor de PI3-K), mas não por PD98059 (inibidor de MEK/ERK 1/2). Ambos os protocolos de tratamento com estradiol induziram a fosforilação/ativação da proteína quinase B (PKB/Akt) e a fosforilação/inativação da glicogênio sintase quinase-3β (GSK-3β). Em um estudo similar, o imunoconteúdo do receptor estrogênico ERα diminuiu após POG em culturas tratadas tanto com estradiol quanto veículo, enquanto que o receptor ERβ aumentou apenas nas culturas tratadas com estradiol expostas ou não à POG. Não foram observadas alterações no imunoconteúdo dos transportadores de glutamato (EAATs) em nenhum dos tratamentos in vitro. Em fatias de hipocampo de cérebro de ratas ovariectomizadas que receberam reposição de estradiol, a morte celular foi reduzida em comparação ao grupo de ratas que não recebeu a reposição hormonal. Neste mesmo modelo, observou-se que a POG aumentou a produção de radicais livres nos dois grupos, porém não foram observadas diferenças na capacidade antioxidante total. Por outro lado, a reposição de estradiol evitou a redução nos conteúdos de triptofano e tirosina causada por POG. No modelo in vivo, o cérebro de ratos neonatos foi protegido contra a hipóxia-isquemia pelo précondicionamento hipóxico. Em paralelo, o pré-condicionamento aumentou o imunoconteúdo dos transportadores de glutamato EAAT2 e do receptor estrogênico ERα em córtex e diminuiu os níveis de EAAT2 em estriado, mas não afetou os níveis de EAAT1 e ERβ. Já no modelo in vitro de pré-condicionamento, nas culturas organotípicas de hipocampo pré-condicionadas, 15 min de POG induziu tolerância acentuada a um período subseqüente de 45 min de POG, porém não foram detectadas alterações nos transportadores de glutamato nem nos receptores estrogênicos. Juntos, os resultados sugerem que na isquemia a neuroproteção induzida por estrógeno pode envolver a via de sinalização celular da fostatidil inositol 3-quinase (PI3-K), a prevenção do dano oxidativo a proteínas e a regulação dos receptores estrogênicos ERα e ERβ, enquanto que a tolerância à isquemia cerebral induzida por pré-condicionamento pode envolver a regulação dos transportadores de glutamato EAAT2 e receptores estrogênicos ERα.

Estrogênios em águas naturais e tratadas da região de Jaboticabal - São Paulo

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Reproductive cycle, ovarian development, and vertebrate-type steroids profile in the freshwater prawn Macrobrachium rosenbergii

This study is intended to characterize the ovarian development and hemolymph vertebrate-type steroids concentration during the reproductive cycle of the freshwater prawn, Macrobrachium rosenbergii. A five-stage classification based on the external observation of the ovary's size and color as seen through the tegument was used. The results showed the existence of a direct correspondence between the ovarian stages and the gonadosomatic index, the oöcyte diameter, and the characteristics of ovarian histology. In each stage total bleeding of the prawns was conducted and the hemolymph concentrations of 17β-estradiol (E 2), testosterone (T) and 17α-hydroxyprogesterone (17-OHP; conjugated and unconjugated) were determined by solid-phase radioimmunoassay (RIA). High levels of unconjugated 17-OHP, relatively constant concentrations of unconjugated T, and null concentration of unconjugated E 2 were found throughout the five stages considered. Nonetheless, low levels of E 2 were determined in all stages, in conjugated (glucoronide) form. The highest levels were obtained in stage II and III (18.14 ± 14.52 pg/ml hemolymph) and progressively declined in the other stages (7.53 ± 6.76 pg/ml hemolymph). These results point out the possible involvement of vertebrate-type steroids in the endocrine regulation of the Macrobrachium rosenbergii's ovarian cycle. To our knowledge this is the first study concerning the vertebrate-like steroid levels throughout the ovarian cycle and is a step needed to characterize the hemolymph profile of these steroids in order to elucidate the possible role in the regulation of the reproductive crustacean cycle.

Tamoxifen inhibits transforming growth factor-α gene expression in human breast carcinoma samples treated with triiodothyronine

Objectives: To examine the effects of triiodothyronine (T3), 17β-estradiol (E2), and tamoxifen (TAM) on transforming growth factor (TGF)-α gene expression in primary breast cancer cell cultures and interactions between the different treatments. Methods and results: Patients included in the study (no.=12) had been newly diagnosed with breast cancer. Fresh human breast carcinoma tissue was cut into 0.3-mm slices. These slices were placed in six 35-mm dishes on 2-ml organ culture medium. Dishes received the following treatments: dish 1: ethanol; dish 2: T3; dish 3: T3+TAM; dish 4: TAM; dish 5: E2; dish 6: E2+TAM. TGF-α mRNA content was normalized to glyceraldehyde-3-phosphate dehydrogenase mRNA levels. All tissues included in this study were positive for estrogen receptor (ER) and thyroid hormone receptor expression. Treatment with T3 for 48 h significantly increased TGF-α mRNA levels compared to controls (15-fold), and concomitant treatment with TAM reduced expression to 3.4-fold compared to controls. When only TAM was added to the culture medium, TGF-α mRNA expression increased 5.3-fold, significantly higher than with all other treatment modalities. Conclusion: We demonstrate that TGF-α mRNA expression is more efficiently upregulated by T3 than E2. Concomitant treatment with TAM had a mitigating effect on the T3 effect, while E2 induced TGF-α upregulation. Our findings show some similarities between primary culture and breast cancer cell lines, but also some important differences: a) induction of TGF-α, a mitogenic protein, by TAM; b) a differential effect of TAM that may depend on relative expression of ER α and β; and c) supraphysiological doses of T3 may induce mitogenic signals in breast cancer tissue under conditions of low circulating E2. ©2008, Editrice Kurtis.

The effects of stressful broodstock handling on hormonal profiles and reproductive performance of rhamdia quelen (Quoy & Gaimard) females

A stressful environment induces cortisol that might affect fish breeding and reproduction. In the present work, which aimed to mimic aquacultural conditions of the jundia (Rhamdia quelen) hatcheries in southern South America, females were submitted to normal or stressful handling and the effects of cortisol on serum levels of 17β-estradiol (E2) and testosterone (T) were determined. In addition, the effect of stress on reproductive parameters such as eggs and swim-up fry production was also measured. Eight females from a group submitted to stressful handling (SH) conditions and eight females from a group with normal handling (NH) conditions were captured for blood sampling at D 0 and at D 1, 10, 20, 30, and 40 of the experiment. A typical cortisol response was observed in the SH females group in that they presented higher cortisol level in contrast to the NH female group, in all days sampled, except at D 0. In the 10th and 20th d, the E2 levels were lower in SH females, but cortisol levels were higher, suggesting an effect of cortisol on E2 production and/or release. Stressful handling appeared to affect both the number and the quality of the gametes because a lower number of oocytes was stripped from SH females, and from SH fertilized eggs, a lower number of viable swim-up fry was obtained to be transferred to earthen larviculture ponds. Taken together, the results indicated that stressful handling of broodstock impairs R. quelen reproduction. © Copyright by the World Aquaculture Society 2008.

The expression of aquaporins 1 and 9 in adult rat epididymis is perturbed by chronic exposure to ethanol

Aquaporins (AQPs), notably AQP-1 and AQP-9, may contribute to reabsorption of fluid and solute across the epididymis. Ethanol is related to be a toxicant affecting directly or indirectly the epididymis and the sperm motility. This study examined the expression of AQP-1 and AQP-9 in adult epididymis of the UChA and UChB 10% (v/v) ethanol-preferring rats, focusing the ethanol-induced hormonal disturbances upon the regulation of these AQPs. Chronic ethanol intake significantly decreased body weight, while UChA and UChB rats displayed a marked loss of epididymal weights. Both ethanol-consuming animals had a severe reduction of testosterone levels, whereas LH and 17β-estradiol were unchanged. Throughout the epididymis, a strong reaction to AQP-1 was observed in myoid and endothelial cells of the UChB ethanol-preferring rats, differently from a moderate intensity in the initial segment of the UChA rats. In addition, AQP-9 showed a strong immunoreaction in the apical membrane of principal cells at initial segment. In cauda epididymis, the level of AQP-9 was reduced along the microvillus projections in both UChA and UChB rats compared to controls. We conclude that chronic ethanol consumption modulates the androgen levels, thereby modifying the expression pattern of AQP-1 and 9 in the epididymis. © 2011 Elsevier Ltd.

Diferenças sazonais no padrão endócrino e ovariano do ciclo estral de novilhas bos taurus indicus (Nelore)

Estrous cycle of eight Nelore heifers were evaluated during different seasons of the year (autumn n=11; winter n=8; spring n=9 and summer n=9) with daily count and measurement of follicles ≥3mm, blood was collected every 12h for LH and progesterone (P4), and after estrous every 3h for LH peak. Five ovariectomized heifers were injected with 17β-estradiol (2μg/kg) every season and blood samples collected every 3h (for 30h) thereafter for LH quantification. The monthly percent body weight difference (Δ%) did not vary among seasons. P4 concentration was higher (p<0.01) and follicle number lower during autumn and summer compared to winter and spring. During winter there were more estrous cycles with three and during summer only cycles with two follicular waves (p<0.01). As LH secretion did not vary despite P4 concentration and as there was negative correlation between higher P4 values and daily percentile variation of photoperiod (Δ%, p<0.01; r= -0.45) it is possible to suppose that there is seasonal variation on luteal cell sensitivity to LH. In the ovariectomized Nelore heifers, the LH basal concentration (without estradiol stimulus, p=0.02) and the LH response to estradiol (p<0.01) were lower during summer, leading to the hypothesis that there is seasonal variation of hypothalamic sensitivity to estradiol. According to the present experiment there are suggestions of seasonal reproduction in Nelore heifers.

Cyp17a1 and cyp19a1 in the zebrafish testis are differentially affected by oestradiol

Oestrogens can affect expression of genes encoding steroidogenic enzymes in fish gonads. However, little information is available on their effects at the protein level. In this context, we first analysed the expression of key steroidogenic enzyme genes and proteins in zebrafish testis, paying attention also to other cell types than Leydig cells. Gene expression was analysed by quantitative PCR on fluorescence-activated cell-sorting fractions coupled or not to differential plating, while protein synthesis was studied by immunohistochemistry using specific antibodies against zebrafish Cyp17a1, Cyp19a1a and Cyp19a1b. Furthermore, we have evaluated the effect of oestrogen treatment (17β-oestradiol (E2), 10 nM) on the localization of these enzymes after 7 and 14 days of in vivo exposure in order to study how oestrogen-mediated modulation of their expression is linked to oestrogen effects on spermatogenesis. The major outcomes of this study are that Leydig cells express Cyp17a1 and Cyp19a1a, while testicular germ cells express Cyp17a1 and both, Cyp19a1a and Cyp19a1b. As regards Cyp17a1, both protein and mRNA seem to be quantitatively dominating in Leydig cells. Moreover, E2 exposure specifically affects only Leydig cell Cyp17a1 synthesis, preceding the disruption of spermatogenesis. The oestrogen-induced suppression of the androgen production capacity in Leydig cells is a major event in altering spermatogenesis, while germ cell steroidogenesis may have to be fuelled by precursors from Leydig cells. Further studies are needed to elucidate the functionality of steroidogenic enzymes in germ cells and their potential role in testicular physiology. © 2013 Society for Endocrinology.

Evaluation of estrogenic, antiestrogenic and genotoxic activity of nemorosone, the major compound found in brown Cuban propolis

Background: Brown propolis is the major type of propolis found in Cuba; its principal component is nemorosone, the major constituent of Clusia rosea floral resins. Nemorosone has received increasing attention due to its strong in vitro anti-cancer action. The citotoxicity of nemorosone in several human cancer cell lines has been reported and correlated to the direct action it has on the estrogen receptor (ER). Breast cancer can be treated with agents that target estrogen-mediated signaling, such as antiestrogens. Phytoestrogen can mimic or modulate the actions of endogenous estrogens and the treatment of breast cancer with phytoestrogens may be a valid strategy, since they have shown anti-cancer activity.Methods: The aim of the present investigation was to assess the capacity of nemorosone to interact with ERs, by Recombinant Yeast Assay (RYA) and E-screen assays, and to determine by comet assay, if the compound causes DNA-damaging in tumoral and non-tumoral breast cells.Results: Nemorosone did not present estrogenic activity, however, it inhibited the 17-β-estradiol (E2) action when either of both methods was used, showing their antiestrogenicity. The DNA damage induced by the benzophenone in cancer and normal breast cells presented negative results.Conclusion: These findings suggest that nemorosone may have therapeutic application in the treatment of breast cancer. © 2013 Camargo et al.; licensee BioMed Central Ltd.

The renin-angiotensin system plays a major role in voiding dysfunction of ovariectomized rats

Aims: The renin-angiotensin system (RAS) plays a major role in cardiovascular diseases in postmenopausal women, but little is known about its importance to lower urinary tract symptoms. In this study we have used the model of ovariectomized (OVX) estrogen-deficient rats to investigate the role of RAS in functional and molecular alterations in the urethra and bladder. Main methods: Responses to contractile and relaxant agents in isolated urethra and bladder, as well as cystometry were evaluated in 4-month OVX Sprague-Dawley rats. Angiotensin-converting enzyme activity and Western blotting for AT1/AT2 receptors were examined. Key findings: Cystometric evaluations in OVX rats showed increases in basal pressure, capacity and micturition frequency, as well as decreased voiding pressure. Angiotensin II and phenylephrine produced greater urethral contractions in OVX compared with Sham group. Carbachol-induced bladder contractions were significantly reduced in OVX group. Relaxations of urethra and bladder to sodium nitroprusside and BAY 41-2272 were unaffected by OVX. Angiotensin-converting enzyme activity was 2.6-fold greater (p < 0.05) in urethral tissue of OVX group, whereas enzyme activity in plasma and bladder remained unchanged. Expressions of AT1 and AT2 receptors in the urethra were markedly higher in OVX group. In bladder, AT1 receptors were not detected, whereas AT2 receptor expression was unchanged between groups. 17β-Estradiol replacement (0.1 mg/kg, weekly) or losartan (30 mg/kg/day) largely attenuated most of the alterations seen in OVX group. Significance: Prolonged estrogen deprivation leads to voiding dysfunction and urethral hypercontractility that are associated with increased ACE activity and up-regulation of angiotensin AT1/AT2 receptor in the urethral tissue. © 2013 Elsevier Inc. All rights reserved.