Social and sexual incentive properties of estrogen receptor alpha, estrogen receptor beta, or oxytocin knockout mice

Social and sexual incentive motivation, defined as the intensity of approach to a social and a sexual incentive, respectively, were studied in female Swiss Webster mice. In the first experiment, the social incentive was a castrated mouse of the same strain as the females, whereas the sexual incentive was an intact male mouse of the same strain. Ovariectomized females were first tested after oil treatment and then after administration of estradiol benzoate + progesterone in doses sufficient to induce full receptivity. The hormones increased sexual incentive motivation while leaving social incentive motivation unaffected. This suggests that sexual incentive motivation in the female mouse is dependent on ovarian hormones. In the next experiment, ovariectomized females were tested with an intact, male estrogen receptor α knockout and its wild type as incentives, first without hormones and then when fully receptive. There were no differences in incentive properties between the wild type and the knockout. In a similar experiment, we used an intact male estrogen receptor β knockout and its corresponding wild type as incentives. The wild type turned out to be a more attractive social incentive than the knockout, while they were equivalent as sexual incentives. Finally, an intact male oxytocin knockout and its wild type were used as incentives. The knockout turned out to be a superior incentive, particularly a superior sexual incentive. The fact that the estrogen receptor β and oxytocin knockouts have incentive properties different from their wild types may be important to consider in studies of these knockouts' sociosexual behaviors.     

Aggression and arginine vasopressin immunoreactivity regulation by androgen receptor and estrogen receptor alpha

In the following study, we asked which steroid receptors regulate aggression and arginine vasopressin (AVP) immunoreactivity (– ir) in several limbic regions. Using spontaneous mutant and knockout mice, we generated a novel cross of mice whose offspring lacked estrogen receptor α (ERα), androgen receptor (AR) or both ERα and AR. The wild-type (WT) males and females were compared with ERα knockout (ERαKO) male, mutated AR (Tfm) male and ERαKO/Tfm (double knockout; DKO) male littermates. Animals were gonadectomized and treated with 17β-estradiol (E2) prior to resident-intruder aggression tests. WT and Tfm males showed aggression whereas WT females, ERαKO and DKO males did not. In the lateral septum, WT and Tfm male brains had significantly denser AVP-ir as compared with WT females and DKO males. ERαKO male brains were intermediate in the amount of AVP-ir present. In the medial amygdala, brains from all genotypes had equivalent AVP-ir, except DKO males, which had significantly less AVP-ir. Overall, the expression of aggressive behavior coincided with AVP-ir in WT, Tfm and DKO males. However, in ERαKO males and WT females, the amount of AVP-ir was not associated with resident-intruder aggression. In sum we have shown that E2 acts via ERα to regulate aggression in male mice. In contrast both ERα and AR contribute to AVP-ir in limbic brain regions.     

The roles of membrane estrogen receptor subtypes in modulating dopamine transporters in PC-12 cells

The effects of 17β-estradiol (E₂) on dopamine (DA) transport could explain gender and life-stage differences in the incidence of some neurological disorders. We tested the effects of E₂ at physiological concentrations on DA efflux in nerve growth factor-differentiated rat pheochromocytoma cells that express estrogen receptors (ER) α, ERβ, and G-protein coupled receptor 30 (GPR30), and DA transporter (DAT). DAT efflux was determined as the transporter-specific loss of ³H-DA from pre-loaded cells; a 9–15 min 10⁻⁹ M E₂ treatment caused maximal DA efflux. Such rapid estrogenic action suggests a non-genomic response, and an E₂-dendrimer conjugate (limited to non-nuclear actions) caused DA efflux within 5 min. Efflux dose–responses for E₂ were non-monotonic, also characteristic of non-genomic estrogenic actions. ERα siRNA knockdown abolished E₂-mediated DA efflux, while ERβ knockdown did not, and GPR30 knockdown increased E₂-mediated DA efflux (suggesting GPR30 is inhibitory). Use of ER-selective agonists/antagonists demonstrated that ERα is the predominant mediator of E₂-mediated DA efflux, with inhibitory contributions from GPR30 and ERβ. E₂ also caused trafficking of ERα to the plasma membrane, trafficking of ERβ away from the plasma membrane, and unchanged membrane GPR30 levels. Therefore, ERα is largely responsible for non-genomic estrogenic effects on DAT activity.     

Regulation of α2A-Adrenergic Receptor Expression by Epinephrine in Cultured Astroglia from Rat Brain

Abstract: Epinephrine (Epi) mediates various physiological effects via α_2A-adrenergic receptors (α_2A-ARs). Studies in mice with a point mutation in the gene for α_2A-AR have shown that these receptors are responsible for the centrally mediated depressor effects of α₂-AR agonists. These studies underscore the importance of understanding the basic cellular mechanisms involved in the expression of α_2A-ARs, of which little is known. We use astroglia cultured from the hypothalamus and brainstem of adult Sprague-Dawley rats as a model system in which to study factors that regulate α_2A-AR expression. These cells contain α₂-ARs, which are predominately of the α_2A-AR subtype. Our studies have shown that Epi causes a dose- and time-dependent decrease in steady-state levels of α_2A-AR mRNA and number of α_2A-ARs, effects that are mediated via α₁- and β-adrenergic receptors (α₁-ARs and β-ARs). These effects of Epi on α_2A-AR mRNA and α_2A-AR number are mimicked by activation of protein kinase C or increases in cellular cyclic AMP, which are intracellular messengers activated by α₁-ARs and β-ARs, respectively. Taken together, these results indicate that expression of α_2A-ARs is regulated in a heterologous manner by Epi, via α₁-AR- and β-AR-mediated intracellular pathways.     

Estrogen-mediated neuroprotection against beta-amyloid toxicity requires expression of estrogen receptor alpha or beta and activation of the MAPK pathway

It is well documented that estrogen can activate rapid signaling pathways in a variety of cell types. These non-classical effects of estrogen have been reported to be important for cell survival after exposure to a variety of neurotoxic insults. Since direct evidence of the ability of the estrogen receptors (ERs) alpha and/or beta to mediate such responses is lacking, the hippocampal-derived cell line HT22 was stably transfected with either ERalpha (HTERalpha) or ERbeta (HTERbeta). In HTERalpha and HTERbeta cells, but not untransfected cells, an increase in ERK2 phosphorylation was measured within 15 min of 17beta-estradiol treatment. The ER antagonist ICI 182, 780 (1 microm) and the MEK inhibitor, PD98059 (50 microm) blocked this increase in ERK2 phosphorylation. Treatment of HT22, HTERalpha and HTERbeta cells with the beta-amyloid peptide (25-35) (10 micro m) resulted in a significant decrease in cell viability. Pre-treatment for 15 min with 10 nm 17beta-estradiol resulted in a 50% increase in the number of living cells in HTERalpha and HTERbeta cells, but not in HT22 cells. Finally, ICI 182, 780 and PD98059 prevented 17beta-estradiol-mediated protection. This study demonstrates that both ERalpha and ERbeta can couple to rapid signaling events that mediate estrogen-elicited neuroprotection.     

The anti-inflammatory activity of estrogen in glial cells is regulated by the PKC-anchoring protein RACK-1

It has recently been suggested that estrogen inhibits glial activation and the release of neurotoxic mediators. The mechanisms involved in this anti-inflammatory effect are unclear. We found that an nM concentration of 17-beta estradiol inhibits protein kinaseC-betaII translocation induced by lipopolysaccharide in primary astrocytes. Estradiol treatment did not change the total content of kinaseC-betaII or of lipopolysaccharide receptor, but dose-dependently reduced the levels of receptors for activated C kinases-1 (RACK-1), the anchoring protein involved in protein kinase C (PKC) shuttling. This decrease could thus account for the defective protein kinaseC-betaII activation. Pre-treatment with 1 nmbeta-estradiol, which reduced by approximately 35% the expression of RACK-1, prevented the lipopolysaccharide-induced expression of tumour necrosis factor-alpha mRNA and of the inducible form of nitric oxide (NO) synthase. As a consequence, the production of tumour necrosis factor-alpha and NO were decreased. An antisense oligonucleotide for RACK-1 also reduced tumour necrosis factor-alpha and nitric oxide production on lipopolysaccharide stimulation. These results demonstrate that estrogen reduction of the RACK-1 expression, leading to a defective protein kinase-C activation counteracts the inflammatory response in astrocytes.     

Cellular localization of androgen and estrogen receptors in mouse-derived motoneuron hybrid cells and mouse facial motoneurons

The ability of gonadal steroid hormones to augment axonal regeneration after peripheral nerve injury has been well established in rat and hamster motoneuron systems, and provides a foundation for the use of these agents as neurotherapeutics. With the advent of mouse genetics and the availability of transgenic and knockout mice, the use of mice in studies of neuroprotection is growing. It has recently been demonstrated that both androgens and estrogens rescue motoneurons (MN) from injury in mouse-derived motoneuron hybrid cells in vitro and mouse facial motoneurons (FMN) in vivo (Tetzlaff et al. [2006] J Mol Neurosci 28:53-64). To elucidate the molecular mechanisms of these effects, the present study examined the cellular localization of androgen and estrogen receptors in mouse MN in vitro and in vivo. Immunoblotting and immunocytochemistry studies established the presence of androgen receptor (AR) and estrogen receptor alpha/beta in immortalized mouse motoneuron hybrid cells and AR and estrogen receptor alpha in mouse FMN.     

Suppression by 17beta-estradiol of monocyte adhesion to vascular endothelial cells is mediated by estrogen receptors

Several observational studies have shown that estrogen replacement therapy decreases cardiovascular mortality and morbidity in postmenopausal women. However, The Women's Health Initiative (WHI) study has found that women receiving estrogen plus progestin had a significantly higher risk of breast cancer, coronary heart disease, stroke, and pulmonary embolus. In the present study, we examined whether estrogen prevents mechanisms that relate to plaque formation by inhibiting monocyte adhesion to endothelial cells. ECV304 cells, an endothelial cell line that normally expresses minimal estrogen receptor (ER)alpha, were transfected with an ERalpha expression plasmid. Treatment with tumor necrosis factor (TNF)-alpha increased expression of vascular cell adhesion molecule (VCAM)-1 mRNA, activation of nuclear factor-kappaB (NF-kappaB), and U937 cell adhesion in ECV304 cells. These effects of TNF-alpha were not significantly inhibited by pretreatment of native ECV304 cells with 17beta-estradiol (E(2)). In ECV304 cells overexpressing ERalpha, E(2) significantly inhibited the effects of TNF-alpha on NF-kappaB activation, VCAM-1 expression, and U937 cell adhesion. These findings suggest E(2) suppresses inflammatory cell adhesion to vascular endothelial cells that possess functional estrogen receptors. The mechanism of suppression may involve inhibition of NF-kappaB-mediated up-regulation of VCAM-1 expression induced by atherogenic stimuli. E(2) may prevent plaque formation, as first stage of atheroscrelosis through inhibiting adhesion monocytes to endothelial cell. Actions of estrogen replacement therapy can be assessed in terms of densities of functional ERalpha.     

二恶英对雌激素受体的干扰作用

核受体相关的肿瘤,如乳腺癌和前列腺癌的发生、发展主要依赖于性激素的分泌。环境内分泌干扰物如Ⅲ二恶英,可作为雌激素受体的诱导配体,直接或间接地与转录因子相互作用,从而干扰基因的转录。此外,二恶英还能使雌激素受体发生泛素化修饰,促进它的降解,并使雌激素依赖性的基因转录受到抑制,成为内分泌干扰因子。本文综述了二恶英的类雌激素效应、致癌性以及激素信号干扰的最新研究进展。     

Morphological and Biochemical Analyses of Amyloid Plaque Core Proteins Purified from Alzheimer Disease Brain Tissue

Abstract— Amyloid plaque cores were purified from Alzheimer disease brain tissue. Plaque core proteins were solubilized in formic acid which upon dialysis against guan-idinium hydrochloride (GuHCI) partitioned into soluble (∼15%) and insoluble (∼85%) components. The GuHCI-soluble fraction contained β-amyloid_1-40, whereas the GuHCI-insoluble fraction was fractionated into six components by size exclusion HPLC: S1 (>200 kDa), S2 (200 kDa), S3 (45 kDa), S4 (15 kDa), S5 (10 kDa), and S6 (5 kDa). Removal of the GuHCI reconstituted 10-nm filaments composed of two intertwined 5-nm strands. Fractions S5 and S6 also yielded filamentous structures when treated similarly, whereas fractions S1–S4 yielded amorphous aggregates. Chemical analysis identified S4–S6 as multimeric and monomeric β-amyloid. Immunochemical analyses revealed α₁-antichymotrypsin and non-β-amyloid segments of the β-amyloid precursor protein within fractions S1 and S2. Several saccharide components were identified within plaque core protein preparations by fluorescence and electron microscopy, as seen with fluores-cein isothiocyanate-and colloidal gold-conjugated lectins. We have shown previously that this plaque core protein complex is more toxic to neuronal cultures than β-amyloid. The non-β-amyloid components likely mediate this additional toxicity, imposing a significant influence on the pathophysiology of Alzheimer disease.     

Phytosterol from the Callus of Stevia Rebaudiana Bertoni

We investigated the effect of 17β-estradiol (E2) on the expression of daintain/AIF-1, a marker of activated macrophages, in RAW264.7. E2 upregulated the protein and mRNA levels of daintain/AIF-1 in similar manners under physiological concentrations of 10^?11 M to 10^?7 M. The application of ICI 182,780, an estrogen receptor (ER) antagonist, attenuated E2-induced daintain/AIF-1 production, suggesting the involvement of ER in this process.     

MLT抑制E2诱发的大鼠垂体PRL瘤的增生涉及雌激素受体的作用

目的：探讨褪黑素（melatonin,MLT）抑制17-β-雌二醇（17-β-estradiol,E2）诱发垂体催乳素（prolactin,PRL）瘤的增生及其机制的初始阶段,MLT对雌激素受体的作用。方法：在体实验采用每日定时给各组SD大鼠分别皮下注射不同浓度的MLT,建立MLT抑制E2诱发的垂体PRL瘤增生的动物模型。离体实验采用原代培养细胞原位杂交方法,探讨垂体PRL瘤细胞MLT受体的表达、MLT对雌激素受体（ER）表达的作用;应用电泳迁移率改变（EMSA）的方法,观察MLT对雌激素受体（ER）与雌激素反应元件（ERE）结合的效应。结果：每只大鼠每日定时皮下注射0．25或0．50mg MLT能显著抑制E2诱发的垂体PRL瘤的增生（分别P〈0．01、P〈0．05）;F4诱发的垂体PRL瘤细胞内有MLT受体MLT1a和MLT1b;给0．25mg／day／rat MLT组的大鼠垂体PRL瘤细胞内ER的表达显著减少（P〈0．01）、ER与ERE的结合量显著降低（P〈0．01）。结论：一定剂量的MLT能显著抑制E2诱发的SD大鼠垂体PRL瘤的增生,其作用机制之一可能与MLT抑制ER的表达、及其部分阻断ER与ERE的结合有关。     

Inhibition of environmental estrogen-induced proliferation of human breast carcinoma MCF-7 cells by flavonoids

Summary In the present study, we evaluated the individual and combined effects of environmental estrogens and flavonoids on the proliferation of human breast carcinoma MCF-7 cells. These compounds are as follows: (1) pharmaceutical chemicals such as diethylstilbestrol, 17α-ethynylestradiol (17ES), tamoxifen, mestranol, and clomiphene, (2) industrial chemicals such as bisphenol A (BisA), 4-octylphenol (OP), 4-nonylphenol (NP), andp,p′-biphenol, and (3) flavonoids such as daidzein (D), genistein (G), quercetin (Q), and luteolin (L). We found that nanomolar concentrations of 17ES, BisA, OP, and NP were sufficient to stimulate the proliferation of MCF-7 cells. Among then, 1 μM BisA exhibited cell proliferation-stimulating activity as strong as 10 nM 17β-estradiol; and D and G exhibited cell proliferation-stimulating activity at 10 nM. On the other hand, Q and L exhibited cell proliferation-inhibiting activity. We also found that 10 nM flavonoids, such as D, G, Q, and L, were able to inhibit the proliferation-stimulating activity in MCF-7 cells by 1 μM environmental estrogens.     

Subunit Structure of α-Bungarotoxin Binding Component in Mouse Brain

Abstract: The α-bungarotoxin binding component in mouse brain was purified by affinity chromatography with toxin-Sepharose, gel-chromatography on Sepharose 6B, and ion-exchange chromatography with DE52 resin. The iodinated product of the last step produced one major and one minor band on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The molecular weight of the minor peak was twice as large as that of the major one. The iodinated product could bind α-bungarotoxin, and this binding was inhibited by a nicotinic antagonist, d -tubocurarine, which demonstrated that the iodinated product was a true α-bungarotoxin binding component. The molecular structure of the product was analysed by cross-linking followed by SDS-PAGE. The results fitted the model for an α-bungarotoxin binding component in the mouse brain composed of six identical or very similar subunits of 51,000-52,000. One subunit carrying the binding site for toxin bound one molecule of toxin. This subunit structure of an α-bungarotoxin binding component in the brain is discussed in comparison with that of a nicotinic acetylcholine receptor in the electric organ.     

Phorbol Esters Mimic α-Adrenergic Potentiation of Serotonin N-Acetyltransferase Induction in the Rat Pineal

alpha-Adrenergic stimulation of the rat pineal gland is known to stimulate phosphatidylinositol turnover and to potentiate the induction of serotonin N-acetyltransferase (SNAT) activity evoked by submaximal beta-adrenergic stimulation. In some (other) systems tumor-promoting phorbol esters are known to mimic physiologic stimulation and to enhance specifically the activity of protein kinase C. Here it is shown that phorbol esters specifically mimic the potentiating effect of alpha-adrenergic stimulation on SNAT activity in the rat pineal. These effects contribute to the argument for a role for phosphatidylinositol turnover and protein kinase C in mediating alpha-adrenergic stimulation.     

Effects of human apolipoprotein E isoforms on the amyloid beta-protein concentration and lipid composition in brain low-density membrane domains

Apolipoprotein E4 (apoE4) encoded by epsilon 4 allele is a strong genetic risk factor for Alzheimer's disease (AD). ApoE4 carriers have accelerated amyloid beta-protein (A beta) deposition in their brains, which may account for their unusual susceptibility to AD. We hypothesized that the accelerated A beta deposition in the brain of apoE4 carriers is mediated through cholesterol-enriched low-density membrane (LDM) domains. Thus, the concentrations of A beta and various lipids in LDM domains were quantified in the brains of homozygous apoE3 and apoE4 knock-in (KI) mice, and in the brains of those mice bred with beta-amyloid precursor protein (APP) transgenic mice (Tg2576). The A beta 40 and A beta 42 concentrations and the A beta 42 proportions in LDM domains did not differ between apoE3 and apoE4 KI mice up to 18 months of age. The A beta 40 concentration in the LDM domains was slightly, but significantly higher in apoE3/APP mice than in apoE4/APP mice. The lipid composition of LDM domains was modulated in an apoE isoform-specific manner, but its significance for A beta deposition remains unknown. These data show that the apoE isoform-specific effects on the A beta concentration in LDM domains do not occur in KI mouse models.     

Elevation of Striatal Dopamine Receptors by Estrogen: Dose and Time Studies

Administration to male rats of a single dose of 17 beta-estradiol valerate (8-500 micrograms/rat) or implantation of a pellet containing 17 beta-estradiol (0.5-50 mg/rat) increased serum 17 beta-estradiol levels in a dose-dependent relationship when measured on the sixth day after administration. At the same time, after these doses, the serum rat prolactin (rPRL) levels were doubled and the striatal 3,4-dihydroxyphenylethylamine (DA, dopamine) receptor densities were increased 20%. A single dose of 17 beta-estradiol valerate of 4 micrograms/rat or less did not alter serum 17 beta-estradiol or rPRL levels or the striatal DA receptor density. After the single injection of 17 beta-estradiol valerate (125 micrograms/rat) the serum 17 beta-estradiol levels peaked at 1 day, the serum rPRL levels peaked at 2 days, and the striatal DA receptor density elevation peaked from 4 to 8 days. Implantation of a pellet containing 17 beta-estradiol (25 mg/rat) produced a constant elevation of serum 17 beta-estradiol levels from 1 to 10 days. Whereas the serum rPRL levels were continuously elevated about two-fold, the densities of the striatal DA receptors were increased significantly by 20-25% only from 4 to 8 days after pellet implantation. These results indicate that striatal DA receptor density rises and returns to control levels during the constant elevation of serum 17 beta-estradiol and rPRL levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Estradiol protects against ATP depletion, mitochondrial membrane potential decline and the generation of reactive oxygen species induced by 3-nitroproprionic acid in SK-N-SH human neuroblastoma cells

Mitochondria are recognized as modulators of neuronal viability during ischemia, hypoxia and toxic chemical exposure, wherein mitochondria dysfunction leading to ATP depletion may be a common pathway of cell death. Estrogens have been reported to be neuroprotective and proposed to play a role in the modulation of cerebral energy/glucose metabolism. To address the involvement of 17beta-estradiol preservation of mitochondrial function, we examined various markers of mitochondrial activity in human SK-N-SH neuroblastoma cells exposed to 3-nitroproprionic acid (3-NPA), a succinate dehydrogenase inhibitor which uncouples oxidative phosphorylation. 3-NPA (10 mM) significantly increased ATP levels at 2 h then caused a 40% and a 50% decrease in ATP levels from baseline when treated for 12 h and 24 h, respectively. 3-NPA also induced significant increases in levels of cellular hydrogen peroxide and peroxynitrite at 2 h and a 60% decrease in mitochondrial membrane potential (MMP) at 12 h exposure. 17beta-Estradiol (17beta-E(2)) pretreatment restored the ATP level back to 80% at 12 h of that in control cells treated with 3-NPA but without E(2), blunted the effect of 3-NPA on MMP and reactive oxygen species levels. The present study indicates that 17beta-E(2) can preserve mitochondrial function in the face of inhibition of oxidative phosphorylation.     

Characterization of the Binding of Amyloid-β Peptide to Cell Culture-Derived Native Apolipoprotein E2, E3, and E4 Isoforms and to Isoforms from Human Plasma

Abstract: The ε4 allele of apolipoprotein E (apoE, protein; APOE, gene) is a major risk factor for Alzheimer's disease (AD). Genetically, the frequency of the ε4 allele is enriched in early-onset sporadic, late-onset familial, and common late-onset sporadic AD. ApoE is found in the extracellular amyloid-β (Aβ) deposits that are characteristic features of AD. In this study, we examined the interaction between Aβ and apoE isoforms. The apoE isoforms used in this study were either produced by stably transfected Chinese hamster ovary cells (CHO) or were from human plasma. We report that when similar concentrations of the apoE isoforms were used, native nonpurified apoE3 from recombinant CHO-derived sources bound Aβ, but apoE4 did not. In fact, in our system, binding of recombinant apoE4 to Aβ was never detectable, even after incubation for 4 days. Furthermore, using the same assay conditions, native apoE2, like apoE3, binds Aβ avidly. Furthermore, when human plasma apoE isoforms are tested in Aβ binding experiments, apoE3 bound Aβ more avidly than apoE4, and a major apoE/Aβ complex (the 40-kDa form) was observed with plasma apoE3 but not apoE4. These data extend our understanding of apoE isoform-dependent binding of Aβ by associating apoE2 with efficient apoE/Aβ complex formation and demonstrate that native apoE3 (whether recombinant or derived from human plasma) forms sodium dodecyl sulfate-stable apoE/Aβ complexes more readily than native apoE4. The different Aβ-binding properties of native apoE4 versus native apoE3 provide insight into the molecular mechanisms by which the APOE ε4 allele exerts its risk factor effects in AD.     

膜雌激素受体介导一氧化氮合酶活性增高的快速非基因效应

实验利用新生小牛胸主动脉内皮细胞(BAECs)作为模型,观察17β-雌二醇(E2)、E2BSA对BAECs中内皮型一氧化氯合酶(eNOS)的快速激活作用,并探讨了丝裂素活化蛋白激酶(MAPK)信号通路在其中的作用。结果显示,不同浓度的E2(0．001—1lμmol/L)作用于BAECs l5 min均能快速激活eNOS;0．01μmol/L浓度的E2作用于BAECs,5min即能激活eNOS,15min达到最大效应,随后eNOS快速失活;E2BSA(17．5ng／m1)作用于BAECs,15min同样可激活eNOS。E2、E2BSA激活eNOS的作用均能被雌激素受体(ER)拮抗剂tamoxifen(0．1μmol/L)或MAPK激酶特异抑制剂PD98059(50μmol/L)所阻断。放线菌素D(25μg/ml)不能阻断E2、E2BSA对eNOS的激活作用。E2(0．01μmol/L)、E2BSA(17．5ng/ml)作用于BAECs l5 min后可明显促进p42／p44磷酸化MAPK蛋白表达,而对p42／p44 MAPK总蛋白表达无影响。Tamoxifen可部分阻断E2;E2BSA激活p42／p44磷酸化MAPK的作用。这些结果提示,BAECs膜上可能存在膜雌激素受体(membrane estrogen receptor,mER),E2、E2BSA作用于mER后可通过MAPK信号途径快速激活eNOS。