一氧化氮介导雌激素的骨形成增加作用

背景雌激素的具体骨保护机制目前尚不清楚,一氧化氮可能在雌激素促进骨形成增加中起到一定的作用.目的探讨雌激素治疗对卵巢切除大鼠血浆硝酸盐/亚硝酸盐水平的影响.设计随机对照的试验.单位上海市杨浦区中心医院骨科和同济医院大学附属协和医院骨科.材料实验在同济医科大学动物实验中心完成,选用3个月龄清洁级健康雌性SD大鼠36只,体质量220～245g,由同济医科大学动物实验中心提供.干预12只SD大鼠完整切除双侧卵巢,设为卵巢切除组;另12只暴露双侧卵巢而不予以切除,设为对照组;雌激素治疗组12只切除双侧卵巢后即刻及后每隔2周皮下注射苯甲酸雌二醇125μg.主要观察指标通过免疫组织化学染色方法检测一氧化氮合成酶在骨组织中的表达,双能X射线测定骨矿密度值,图象分析系统进行骨形态学计量学测量,光密度法测定血浆硝酸盐/亚硝酸盐水平.结果卵巢切除导致血浆硝酸盐/亚硝酸盐水平及骨矿密度值、小梁骨体积等骨形态学计量学参数显著下降.手术后6周,对照组和卵巢切除组平均血浆硝酸盐/亚硝酸盐水平分别为(22.4±1.7),(16.2±3.7)μmol/L;骨矿密度值分别是(0.245±0.030)g/cm2和(0.189±0.030)g/cm2;小梁骨体积分别为(31.97±3.50)%和(17.14±4.20)%,两组之间差异均有显著性意义(P＜0.01).雌激素治疗抑制了卵巢切除导致的这些变化,雌激素治疗组平均血浆硝酸盐/亚硝酸盐水平为(21.9±3.5)μmol/L,骨矿密度值为(0.234±0.020)g/cm2,小梁骨体积为(26.53±1.63)%,与卵巢切除组比较,均有显著性升高(P＜0.01);与对照组比较,差异均无显著性意义(P＞0.05).一氧化氮合成酶免疫活性信号在成骨细胞内测得,雌激素治疗组一氧化氮合成酶信号较卵巢切除组也显著性增强(P＜0.01).结论雌激素通过诱导一氧化氮的产生而刺激骨形成,一氧化氮是雌激素诱导骨形成增加的介导剂.

Effect of nitrogen monoxide mediated with estrogen on bone formation

BACKGROUND: Protective mechanism of estrogen on bone formation is not clear. Nitrogen monoxide(NO) induced by estrogen may have a certain effect on bone formation.OBJECTIVE: To investigate the effects of estrogenic treatment on levels of plasma nitrate/nitrite in ovariectomied rats.DESIGN: Randomized controlled trial.SETTING: The department of Orthopaedics of Central Hospital, Yangpu District, Shanghai.PARTICIPANTS: This experiment was performed in the Animal Experimental Center of Tongji Medical University. A total of 36 healthy clean female Sprague-Dawley(SD) rats, aged 3 months old, weighing 220 - 245 g,were provided by the Animal Experimental Center of Tongji Medical University.INTERVENTIONS: Twelve SD rats were given bilateral ovariectomy completely, as ovariotomy group; Twelve SD rats were treated with their bilateral ovary exposed but not resected, as control group, another 12 SD were carried ovocylin every two weeks, as estrogen treated group.-MAIN OUTCOME MEASURES: Expression of NO synthetic enzyme in bone tissue was measured with the method of immunohistochemistry staining;The bone mineral density(BMD) was measured with dual energy X-ray; Bone morphological and metrological measurement was made with image analysis system; The levels of plasma nitrate/nitrite were detected with optical density method.RESULTS: Ovariectomy induced significantly the levels of plasma nitrate/nitrite, BMD, the yolume of trabecular bone as well as other bone morphological and metrological parametes. Six weeks after operation, the mean levels of plasma nitrate/nitrite in the control and ovariectomy groups were (22.4 ± 1.7 ) μmol / L and ( 16.2 ± 3.7 ) μmol / L, respectively; the value of BMD were(0. 245 ± 0. 030) g/cm2 and(0. 189 ± 0. 030) g/cm2, respectively, volume of trabecular bone were (31.97±3.50)% and(17.14± 4.20) %, respectively. The differences between the two groups was significant( P ＜ 0. 01) . Estrogen inhibited these changes induced by ovariectomy. The mean levels of plasma nitrate/nitrite, value of BMD and volume of trabecular bone in the estrogen-treated group were(21.9 ±3.5) μmol/L,(0. 234 ± 0. 020) g/cm2 and(26.53 ± 1.63)% , respectively, which had significant increase as compared with those in ovariectomy group( P ＜ 0.01 ),and the differences was not significant as compared with those in control group ( P ＞ 0.05) . Immunoreactivity signals of NO synthesis were detected in osteoblasts. The expression of immunoreactivity signals of NO synthetic enzyme in the estrogen-treated group was significantly strengthened as compared with those of ovariectomy group( P ＜ 0.01).CONCLUSION: Estrogen stimulates bone formation by inducting NO production. NO is a mediator which strengthens estrogen-induced bone formation.