雌激素受体α和β在不同雌激素干预大鼠骨代谢中的表达

应用雌性大鼠的骨质疏松模型,通过骨密度(BMD)检测、RT-PCR和Westernblot等技术观察去卵巢(Ovariectomy,OVX)、结合性雌激素(ConjugatedEquineEstrogens,CEE)和戊酸雌二醇(EstradiolValerate,EV)对大鼠松质骨骨量以及松质骨中雌激素受体(ER)α和βmRNA和蛋白表达的影响,探讨两受体亚型在介导雌激素参与松质骨代谢的不同作用机制以及不同来源雌激素对ERα和ERβ表达的差异性调节。40只7-8周龄的雌性Sprague-Dawley大鼠,在观察动情周期后随机分成四组:对照组(Control,n=10)、去卵巢组(Ovariectomy,OVX,n=10)、去卵巢后结合性雌激素治疗组(CEE,n=10)和去卵巢后戊酸雌二醇治疗组(EV,n=10)。对照组大鼠行假手术,其余三组行去卵巢手术。术后48天(12个动情周期),对照组和OVX组用生理盐水喂养12天(3个动情周期),CEE组和EV组分别用药物的生理盐水溶液喂养12天。结果显示:在对照组中,大鼠松质骨ERα的蛋白表达水平显著性高于ERβ蛋白表达水平,而ERα的mRNA表达水平显著性低于ERβmRNA水平。与对照组相比,OVX组大鼠松质骨中ERα的蛋白表达水平显著性降低,ERαmRNA表达水平显著性增加,而ERβ蛋白和mRNA的表达水平均显著性增加。与OVX组相比,CEE组大鼠松质骨中ERβ蛋白和mRNA的表达水平均显著性下降,而EV组大鼠松质骨中ERα蛋白表达显著性上升,ERαmRNA表达显著性下降,ERβ蛋白表达显著性下降。此外,OVX大鼠松质骨的骨密度下降均可通过应用CEE和EV得到显著性改善。上述结果提示:⑴ERα可能是大鼠松质骨中优势表达的受体亚型,在介导雌激素参与松质骨代谢中起着主导作用。⑵不同来源雌激素可能侧重不同的ER亚型途径产生骨保护效应。     

雌性大鼠去卵巢模型中脑神经内分泌信号异常传导的机理

目的比较正常大鼠和去卵巢大鼠脑内主要神经信息分子的种类和含量,以观察生理和病理状态下,神经内分泌信号传导通路的异同,初步探讨卵巢(雌激素)对神经内分泌信号传导机制。方法观察大鼠脑组织神经元细胞病理形态,运用高效液相色谱-荧光检测器定量检测不同脑区及血清中肾上腺素(E)、去甲肾上腺素(NE)、多巴胺(DA)、5-羟色胺(5-HT)、5-羟基吲哚乙酸(5-HIAA)及高香草酸(HVA)的含量变化。结果脑组织HE染色显示OVX组大鼠脑内神经元退化比假手术组明显。与假手术组相比,OVX组大鼠的NE、E含量降低,差异具有统计学意义的区域分别为海马和血清;HVA在丘脑中含量比假手术组升高;DA含量在皮质区比假手术组下降。与假手术组比较,OVX组在海马和小脑区5-HT含量上升,而5-HIAA含量下降;在皮质、丘脑和血清中,OVX组5-HT含量较假手术组下降,而5-HIAA含量升高。结论去卵巢大鼠的雌激素水平低下状态可能引起脑组织携带的主要信息分子(经典神经递质、氨基酸类递质)释放或合成发生异常,因此去卵巢模型大鼠可以作为一种神经内分泌信号异常的载体,为围绝经期综合征的信号传导的研究提供了一种新的思路和方法。     

人参皂甙Rg1对去卵巢帕金森病模型大鼠黑质多巴胺能神经元的保护作用

目的：探讨人参皂甙Rg1对6-羟基多巴（6-OHDA）制备的去卵巢（OVX）帕金森病（PD）模型大鼠黑质（SN）多巴胺能神经元的保护作用及其可能机制。方法：应用6-OHDA制备的OVX PD模型大鼠,侧脑室给予Rg1或雌激素。免疫组织化学染色酪氨酸羟化酶（TH）阳性神经元和Bcl-2蛋白。Perls’铁染色检测SN铁含量。结果：①Rg1或雌激素可抑制阿朴吗啡诱导的PD大鼠旋转行为;②在损毁侧SN,Rg1或雌激素用药组TH阳性神经元数量较6-OHDA组显著增多;③6-OHDA组损毁侧SN内铁含量较健侧明显升高,应用Rg1或雌激素后,SN铁含量较模型组明显减少;④与6-OHDA模型组相比,Rg1及雌激素均可增加损毁侧大鼠SN内Bcl-2蛋白表达。结论：人参皂甙Rg1具有类雌激素样作用,对OVX PD模型大鼠黑质DA能神经元有明显的保护作用,其作用机制可能与降低铁负载和抗凋亡有关。     

雌激素膜性受体GPR30在生后雌性大鼠海马内的发育学表达与细胞内定位研究

研究表明雌激素通过其受体对海马神经元的发育和可塑性以及学习记忆、认知、情绪等高级脑功能发挥了重要调节作用。GPR30是近年才鉴定的一种雌激素受体,它在海马内的表达和功能研究尚属空白。本实验应用免疫组化及免疫电镜技术,对GPR30在生后不同发育阶段大鼠海马内的表达及其免疫阳性产物在神经元内的定位进行了初步研究,结果显示GPR30免疫阳性产物主要位于海马CA区的锥体层神经元与齿状回颗粒层的神经元内,其表达水平随发育呈增加趋势。     

慢性间断性低氧大鼠认知功能和脑胆碱能神经元的进行性变化

目的：探讨慢性间断性低氧（CIH）大鼠认知功能的进行性变化及其与脑胆碱能神经元变化的关系。方法：成年雄性SD大鼠40只,随机均分为对照组、慢性间断性低氧1,3,5周组。应用Morris水迷宫检测认知功能的变化;利用HE染色在光镜下计数前额叶皮层和海马坏死神经元数;利用免疫组化方法检测前额叶皮层和海马胆碱乙酰转移酶（ChAT）阳性表达。结果：CIH各组大鼠学习记忆能力呈进行性下降趋势;与对照组比较,CIH5w组出现明显学习记忆功能障碍（P〈0.05）。CIH各组前额叶皮层和海马变性坏死神经元数增多,且随低氧时间延长,上述改变呈慢性进行性加重趋势。CIH各组前额叶皮层和海马ChAT阳性表达逐渐下降;与对照组比较,CIH3w组和CIH5w组前额叶皮层和海马ChAT阳性表达明显减少,差异具有显著性（P〈0.05）。结论：慢性间断性低氧大鼠认知功能进行性下降与前额叶皮层和海马神经元病理性损伤、ChAT表达进行性减少有关。     

电针足三里穴对糖尿病胃轻瘫大鼠延髓多巴胺能神经元和 星形胶质细胞活性的影响

目的:研究电针足三里穴对糖尿病胃轻瘫大鼠延髓多巴胺能神经元内酪氨酸羟化酶(tyrosine hydroxylase,TH)和星形胶质细胞内胶质原纤维酸性蛋白(Glial Fibrillary Acidic Protein,GFAP)表达的影响。方法:32只实验大鼠分为空白对照(空白)组、糖尿病胃轻瘫模型(模型)组、模型组+电针足三里穴(足三里)组和模型组+电针非经非穴(非经非穴)组(每组8只)。模型制备采用腹腔注射5%四氧嘧啶和熟地灌胃诱导的方法。实验3周后取大鼠延髓进行抗TH和抗GFAP的单一和双重免疫组化染色,观察并记数TH和GFAP在延髓内的表达。结果:与空白组比较,各实验组TH阳性多巴胺能神经元和GFAP阳性星形胶质细胞集中表达于延髓迷走孤束复合体内,有明显的定位特点;高倍镜下观察到TH阳性神经元周围有大量GFAP阳性星形胶质细胞包绕。各组TH和GFAP表达以模型组最高;而足三里组TH阳性多巴胺能神经元数量明显减少(31.3±4.4→16.8±3.2),GFAP阳性产物表达明显降低(113.8±7.6→95.4±8.4),且它们之间有统计学意义(P<0.01);非经非穴组与模型组之间差异没有统计学意义。结论:针刺调节糖尿病胃运动功能障碍大鼠与其调控延髓多巴胺能神经元及其周围的星形胶质细胞功能活动有关。     

染料木素对卵巢切除大鼠学习记忆能力的影响

目的：探讨染料木素对卵巢切除大鼠学习记忆能力的影响及作用机制。方法：将40只SD雌性大鼠随机分为用假手术组、去卵巢对照组、染料木素高剂量、低剂量组、17β-雌二醇组,切除卵巢建立学习和记忆能力受损的模型。灌胃给药6周后Morris水迷宫测定各组大鼠学习记忆能力,免疫组化法观察大鼠海马微管相关蛋白（tau蛋白）阳性表达情况,测定大鼠脑组织中乙酰胆碱酯酶（AchE）、乙酰胆碱转移酶（ChaT）、超氧化物歧化酶（SOD）的活性及丙二醛（MDA）的含量,观察海马组织超微结构变化。结果：大鼠切除卵巢后Morris水迷宫测定的学习记忆能力显著下降,微管相关蛋白（tau蛋白）异常磷酸化阳性表达率增高,前脑皮质中超氧化物歧化酶（SOD）、乙酰胆碱转移酶（ChaT）活性降低,丙二醛（MDA）含量、乙酰胆碱酯酶（AchE）活性增高。低剂量的染料木素可以发挥类雌激素样作用,改善去卵巢大鼠的以上症状。结论：染料木素对卵巢切除导致的学习和记忆能力下降有改善作用,低剂量效果显著,其可能的机制是：抑制了脑内AchE的活性,使乙酰胆碱的降解减少;增强脑组织抗氧化能力;稳定微管相关蛋白（tau蛋白）,降低tau蛋白异常磷酸化水平。     

bFGF对脑缺血再灌注大鼠海马及顶叶皮质神经元的保护作用

目的本实验应用大脑中动脉栓塞（MCAO）模型,观察bFGF对脑缺血再灌注损伤后海马及顶叶皮质中Wnt通路抑制因子Dickkopf-1（DKK-1）和Wnt通路中pCatenin的表达作用的影响,以探讨Wnt通路对缺血性脑损伤的作用机制,为临床治疗缺血性脑血管病提供实验依据。方法应用线栓法制作大鼠局灶性脑缺血再灌注模型,大脑中动脉阻塞1h再灌注损伤24h,采用免疫组织化学SABC法及RT-PCR法检测海马及顶叶皮质CA1区神经元β-Catenin和DKK-1mRNA的表达。结果正常sham组,大鼠海马组织DKK-1 mRNA表达较少,β-Catenin阳性产物在细胞质内有所表达;I／R组,DKK-1 mRNA表达明显增多,β-Catenin在胞质内表达明显减少;bFGF组,大鼠海马组织DKK-1 mRNA表达较I／R组明显减少,而海马细胞质内β-Catenin表达较I／R组明显增加。结论bFGF抑制缺血神经元凋亡,参与DKK-1 mRNA和β-Catenin的调节,对缺血神经元有保护作用。     

电针对去卵巢大鼠学习记忆能力及海马神经元型一氧化氮合酶mRNA表达的影响

目的研究电针对去卵巢大鼠学习记忆能力及海马神经元型一氧化氮合酶（nNOS）mRNA表达的影响。方法采用卵巢切除大鼠模型,造成低雌激素记忆障碍,去势2周后进行电针刺激,连续治疗3个月。Morris水迷宫测试空间学习记忆能力,酶联免疫吸附分析（ELISA）检测血清雌二醇（E2）浓度,实时荧光定量PCR检测检测nNOSmRNA的相对表达量。结果与假手术组比较,模型组大鼠逃避潜伏期时间明显延长,跨越平台次数明显减少,血清E2浓度和海马nNOSmR—NA表达显著降低（P〈O．01）;与模型组比较,电针组和假电针组治疗后逃避潜伏期缩短,跨越平台次数增加,血清E2浓度和海马nNOSmRNA表达均显著升高,电针组升高更明显（P〈O．01）。结论电针能够提高去卵巢大鼠学习记忆能力,其机制可能与升高体内雌激素浓度上调海马nNOSmRNA的表达有关。     

雌激素缺乏对痴呆小鼠学习记忆及海马区细胞增殖和成熟的影响

该文旨在研究雌激素缺乏不同时间段对APP/PS1双转基因小鼠学习记忆及海马区细胞增殖和成熟的影响及探究潜在的机制。将3月龄APP/PS1双转基因AD雌性小鼠行双侧卵巢切除(AD-OVX),以假手术AD小鼠(AD-Sham)及同月龄正常野生型小鼠(WT)作为对照,于术后1周(模拟绝经早期)和3月(模拟绝经中晚期), Morris水迷宫行为测试结果显示,在APP/PS1双转基因AD小鼠中, OVX后1周, AD-OVX组与AD-Sham组比较,其逃避潜伏期、搜索路径以及穿越平台的次数无明显差异(P0.05);而OVX后3月, AD-OVX组小鼠找到平台的时间和搜索路径显著延长(P0.05),穿越平台的次数也相应减少(P0.05);子宫重量结果、EDU细胞增殖状况、老年斑、脑内NeuN蛋白和芳香酶的变化水平分别显示,在APP/PS1双转基因AD小鼠中, OVX后1周, AD-OVX组与ADSham组比较,循环雌激素水平无明显变化;小鼠脑内未见老年斑;小鼠海马区新生阳性细胞数量和NeuN的表达反应性增多(P0.05);此时小鼠脑内芳香酶表达也呈反应性升高(P0.05)。而OVX后3月, AD-OVX组小鼠循环雌激素水平明显降低(P0.05);脑内老年斑显著增加(P0.05);小鼠海马区新生阳性细胞数量和NeuN的表达减少(P0.05);此时小鼠脑内芳香酶水平也显著降低(P0.05)。以上结果说明,雌激素缺乏早期可反应性地增加痴呆小鼠海马区细胞的增殖和成熟,对小鼠学习记忆无影响;但随着雌激素缺乏时间的延长,痴呆小鼠出现学习记忆的损害及海马区细胞增殖和成熟减少;该作用可能与脑内芳香酶水平的变化密切相关。     

Effect of estradiol and soy phytoestrogens on choline acetyltransferase and nerve growth factor mRNAs in the frontal cortex and hippocampus of female rats.

We report here the effects of oral micronized estradiol and soy phytoestrogens on uterine weight, choline acetyltransferase (ChAT) and nerve growth factor (NGF) mRNAs in the frontal cortex and hippocampus of ovariectomized young and retired breeder rats. Within each age category, 15 bilaterally ovariectomized rats were randomized equally into three groups: control (OVX), estradiol (E2), and soy phytoestrogens (SBE). The OVX rats were fed a casein/lactalbumin-based control diet; the E2 rats were fed with the control diet with added estradiol; and the SBE rats were fed with the control diet with added soy phytoestrogens. After 8 weeks of treatment, blood, uteri, frontal cortex, and hippocampus were collected at necropsy. Results showed that the uterine weights and serum estradiol concentrations were significantly higher in the E2 group compared with those in the OVX and SBE groups. In the hippocampus of young rats, E2 treatment resulted in significantly higher NGF mRNA levels than no treatment (OVX), and NGF mRNA levels in the SBE group were intermediate between the E2 and OVX groups. ChAT mRNA levels were significantly higher in the frontal cortex of E2 and SBE-treated retired breeder rats compared to OVX retired breeder rats. There were no differences among treatment groups for ChAT mRNA levels in the frontal cortex of young rats and in the hippocampus of both young and retired breeder rats. Our data suggest that soy phytoestrogens may function as estrogen agonists in regulating ChAT and NGF mRNAs in the brain of female rats.     

Mechanisms of 17beta-estradiol on the production of ET-1 in ovariectomized rats

In order to clarify the mechanism underlying the possible preventive effect of estrogen on atherogenesis, we investigated the role of 17beta-estradiol (E2) in the regulation of endothelin-1 (ET-1) production in ovariectomized rats, which may contribute to atherogenesis. Female Spragure-Dawly rats were randomly divided into three groups: sham-operated group (sham), ovariectomized group (OVX) and 17beta-estradiol replacement group (OVX + E2, 20 microg(-1).kg.d(-1),s.c.). 4 weeks after operation, the plasma concentration of ET-1, clearance of ET-1, functional ECE activity and preproET-1 mRNA expression in aorta were measured. Concentration of plasma ET-1 change from 107.8 +/- 18.3 pg/ml (sham) and 135.5 +/- 27.6 pg/ml (OVX + E2) to 190.7 +/- 25.5 pg/ml (OVX ) (n = 8, p < 0.05). There was no significant difference in the clearance of 125IET-1 among three groups (p > 0.05). Functional ECE activity was increased in OVX group in comparison to that in sham group (p < 0.05). The OVX increased the preproET-1 mRNA expression in sham, whereas treatment with estrogen reversed these changes (p < 0.05). The present study have shown that estrogen down-regulates plasma ET-1 levels by inhibiting the preproET-1 mRNA expression and functional ECE activity. Clearance of ET-1 was not affected. Inhibition of ET-1 production mediated by modulating ECE activity may be one of the novel mechanisms of the protective of estrogens on the cardiovascular system.     

The obesity in bilateral ovariectomized rats is related to a decrease in the expression of leptin receptors in the brain.

We investigated the expression levels of leptin receptors in the brain of ovariectomized (OVX) rats. The mean expression level of ob mRNA in adipose tissues of OVX rats was significantly (P < 0.01) lower than that in the SHAM operation group rats, and the mean body weight of OVX rats was significantly (P < 0.01) greater than that in the SHAM group rats. However, there were no differences between serum leptin concentrations in these two groups. The mean level of leptin receptor (OB-R) mRNA expression in the brain tissue and the mean level of long form type OB-R (OB-RL) mRNA expression in the hypothalamus of the OVX rats were significantly (P < 0.05) lower than those in the SHAM group rats. These changes were cancelled by supplementation with 17 beta-estradiol in OVX rats. These results suggested that not only changes in the expression level of ob mRNA in adipose tissue and the serum leptin concentration but also changes in the OB-R mRNA in the brain are involved in the body weight increase in OVX rats and that a decrease in OB-R makes transmission of signals to suppress the amount of food intake difficult, thus leading to an increase in body weight.     

Estrogen responsiveness of renal calbindin-D28k gene expression in rat kidney

In women, calcium excretion in the urine rises after menopause and falls with estrogen replacement therapy. The amount of calcium lost in the urine following estrogen therapy is less than should occur based on changes in serum calcium and the amount of calcium filtered by the kidney. This suggests there may be a direct effect of estrogen therapy to increase renal calcium reabsorption. Calbindin D_28k is a putative calcium ferry protein located in the distal renal tubules which has been shown to increase transcellular calcium transport. We proposed that estrogen loss after menopause may diminish gene expression of renal calbindin D_28k and subsequently diminish renal calcium reabsorption. We used the ovariectomized rat model of estrogen deficiency to investigate changes at the messenger RNA level of calbindin D_28k in ovariectomized rats (OVX), sham ovariectomized rats (S-OVX), and estrogen treated ovariectomized rats (E-OVX). We have demonstrated that ovariectomy in rats diminishes the gene expression of renal calbindin D_28k. The mRNA levels were approximately three times lower in OVX rats than S-OVX rats. Administration of 17β estradiol to OVX rats produced a significant increase in mRNA level to greater than the S-OVX rats by 4 h. Measurement of serum 1,25 dihydroxyvitamin D₃ showed lower level in OVX rats than S-OVX rats but no significant change in E-OVX animals. In conclusion, our results indicate that estrogen increases renal calbindin D_28k mRNA levels, by a mechanism independent of changes in 1,25 dihydroxyvitamin D₃. This may result in increased expression of calbindin D_28k protein which may have a role in reducing renal calcium excretion. J. Cell. Biochem. 65:340–348. © 1997 Wiley-Liss, Inc.     

Gender related alterations of β-adrenoceptor mechanisms in heart failure due to arteriovenous fistula

This study was undertaken to determine gender related changes in different components of β-adrenoceptor (β-AR) system in response to arteriovenous fistula (AV-shunt), which is known to produce heart failure due to volume overload. AV-shunt was induced in male and female rats for 16 weeks by the needle technique; ovariectomized (OVX) rats treated with or without estrogen were also used. Although AV-shunt for 16 weeks produced cardiac hypertrophy in both sexes, male animals showed cardiac dysfunction whereas cardiac performance was maintained in females. Both β(1) -AR and β(2) -AR protein content and mRNA levels were decreased in male and increased in female hearts post-AV-shunt. The basal adenylyl cyclase (AC) activity was lower in the female heart; however, AC protein content and the increase in epinephrine (EPi)-stimulated AC activity were greater in the female AV-shunt group as compared to males. While AC V/VI and β-arrestin 2 mRNA levels were decreased in males, mRNA level for GRK2 was increased in females post-AV-shunt. In contrast to intact females, AV-shunt OVX animals showed depressed cardiac function, decreased β(1) -AR, β(2) -AR, and AC protein content, as well as reduced EPi-stimulated AC activity. Treatment of OVX rats with 17-β estradiol attenuated the AV-shunt induced changes in β-AR and AC protein content as well as cardiac dysfunction. These results reveal that β-AR signal transduction system in response to AV-shunt is downregulated in males and upregulated in females. Furthermore, estrogen appears to play an important role in the upregulation of β-AR mechanisms and the maintenance of cardiac function in AV-shunt females.     

Regulation of UCP1, UCP2, and UCP3 mRNA expression in brown adipose tissue, white adipose tissue, and skeletal muscle in rats by estrogen

The effects of ovariectomy (OVX) and estrogen substitution on body weight, body composition, food intake, weight gain, and expression of uncoupling proteins (UCPs) in brown adipose tissue (BAT), white adipose tissue (WAT), and skeletal muscle were studied in four groups of rats: (1) Sham-operated rats (N = 8), (2) ovariectomized rats (OVX - E) (N = 8), (3) estrogen-treated OVX rats (OVX + E) (N = 8), and (4) OVX rats on energy restriction (OVX - E + D) (N = 8). OVX was associated with an increase in food intake and body weight gain during a 5-week study period compared to sham-operated rats. The estrogen-substituted rats had a significantly lower food intake and weight gain during the 5 weeks compared to the sham-operated group. However, we also included a nontreated OVX group that was allowed to eat only enough chow to match the weight gain of the sham-operated group. To match the weight gain in the two groups, the OVX group had to consume 16% less chow than the sham-operated group. In BAT, the UCP1 expression was significantly lower in estrogen-deficient rats compared to either intact rats or estrogen-substituted rats, whereas UCP2 and UCP3 mRNA expression was similar in BAT from all four groups. In WAT, both estrogen-deficient groups had significantly lower UCP2 mRNA expression compared to the control rats and estrogen-treated rats; In contrast, the UCP3 mRNA expression in WAT was similar in all four groups. Finally, in skeletal muscle the OVX group on mild energy restriction had reduced UCP3 mRNA expression compared to control, OVX, and estrogen-treated rats. In contrast, the UCP2 mRNA expression in skeletal muscle was similar in all four groups. Thus, the findings that estrogen deficiency is followed by reduced UCP1 expression in BAT and reduced UCP2 expression in WAT in association with weight gain probably caused by a decrease in energy expenditure might indicate that UCPs play a role for the estrogen-mediated changes in body weight and energy expenditure.     

Endothelin-1 contributes to the sexual differences in renal damage in DOCA-salt rats

We investigated whether gender differences in renal damage in DOCA-salt hypertension are associated with effects of ovarian hormones and/or endothelin-1 (ET-1). Renal injuries and renal pre-pro-ET-1 mRNA expression were enhanced in male and female ovariectomized (OVX) DOCA rats versus female DOCA rats. Treatment with estrogen plus progesterone or progesterone, but not estrogen alone, attenuated renal damage and pre-pro-ET-1 mRNA expression in OVX DOCA rats. The ETA antagonist BMS182874 greatly ameliorated renal damage in male and OVX DOCA rats. In conclusion, the ovarian hormones have a protective role on the renal structural alterations in female DOCA rats by modulating effects of ET-1, via ETA receptors.     

Nitric-oxide-dependent pial arteriolar dilation in the female rat: effects of chronic estrogen depletion and repletion

In this study, we compared endothelial nitric oxide synthase (eNOS)-mediated cerebral vasodilating responses in intact female rats, chronically ovariectomized (OVX) rats, and OVX rats treated for 2 weeks with 17beta-estradiol (E(2)). Under anesthesia, using intravital microscopy and a closed cranial window system, pial arteriolar diameter changes were monitored during sequential cortical suffusions of an eNOS-dependent dilator [acetylcholine (ACh)] and a direct NO donor [S-nitrosoacetylpenicillamine (SNAP)]. In separate rats from the same groups, we compared eNOS and caveolin-1 (CAV-1) protein abundance in pial arterioles (via immunofluorescence analyses). In untreated and low-dose E(2)-treated (1.0 microg x kg(-1) x day(-1)) OVX rats, ACh-induced vasodilations were virtually absent. High-dose E(2) treatment (100 microg x kg(-1) x day(-1)) restored ACh-induced pial arteriolar dilations to levels seen in intact females. The vasodilations elicited by SNAP and ADO were unaffected by chronic estrogen changes, indicating no direct estrogen influence on vascular smooth muscle (VSM) reactivity. Pial arteriolar eNOS protein abundance was diminished by ovariectomy and restored by high-dose E(2) treatment. Pial arteriolar CAV-1 expression was higher in OVX versus intact and E(2)-treated OVX females. These results suggest that long-term changes in estrogen directly influence brain eNOS functional activity. The estrogen-related changes in eNOS-dependent vasodilating function appear to be related, in part, to a capacity for E(2) to increase eNOS protein expression and, in part, to an E(2)-associated diminution in endothelial CAV-1 expression.     

Estrogen effects on skeletal muscle insulin-like growth factor 1 and myostatin in ovariectomized rats

Previous work showed that estrogen replacement attenuates muscle growth in immature rats. The present study examined muscle insulin-like growth factor-1 (IGF-1) and myostatin expression to determine whether these growth regulators might be involved in mediating estrogen's effects on muscle growth. IGF-1 and myostatin message and protein expression in selected skeletal muscles from 7-week-old sham-ovariectomized (SHAM) and ovariectomized rats that received continuous estrogen (OVX/E2) or solvent vehicle (OVX/CO) from an implant for 1 week or 5 weeks was measured. In the 1-week study, ovariectomy increased IGF-1 mRNA expression in fast extensor digitorum longus and gastrocnemius muscles; the increase was reversed by estrogen replacement. A similar trend was observed in the slow soleus muscle, although the change was not statistically significant. In contrast to mRNA, muscle IGF-1 protein expression was not different between SHAM and OVX/ CO animals in the 1-week study. One week of estrogen replacement significantly decreased IGF-1 protein level in all muscles examined. Myostatin mRNA expression was not different among the 1-week treatment groups. One week of estrogen replacement significantly increased myostatin protein in the slow soleus muscle but not the fast extensor digitorum longus and gastrocnemius muscles. There was no treatment effect on IGF-1 and myostatin expression in the 5-week study; this finding suggested a transient estrogen effect or upregulation of a compensatory mechanism to counteract the estrogen effect observed at the earlier time point. This investigation is the first to explore ovariectomy and estrogen effects on skeletal muscle IGF-1 and myostatin expression. Results suggest that reduced levels of muscle IGF-1 protein may mediate estrogen's effect on growth in immature, ovariectomized rats. Increased levels of muscle myostatin protein may also have a role in mediating estrogen's effects on growth in slow but not fast skeletal muscle.