脉冲电磁场干预去势雌性大鼠骨代谢的强度窗效应

An intensity window in the effects of pulsed electromagnetic fields on bone metabolism in ovariectomized rats

目的 研究不同强度脉冲电磁场（PEMFs）对去势雌性大鼠骨代谢的影响.方法 将60只10月龄雌性Sprague-Dawley大鼠随机分为空白组、去势组、0.14mT组、O.16mT组、0.18mT组和雌激素组,除空白组行假手术外,其余均切除双侧卵巢以建立骨质疏松模型.术后1周,将0.14mT组、0.16mT组、0.18mT组大鼠暴露于相应的PEMFs下,每日1次,每次60min,为期3个月;雌激素组行雌激素皮下注射.实验期间动态测定大鼠全身骨密度（BMD）,第3个月末处死大鼠并测定相关生化指标和局部骨密度.结果 与空白组相比,其余5组碱性磷酸酶（ALP）活性均显著上升（P〈0.01）,去势组、0.14mT组抗酒石酸酸性磷酸酶5b（TRAP5b）水平显著升高（P〈0.01）;干预至第2个月末,0.14mT组全身骨密度明显低于空白组（P〈0.05）,第3个月末,去势组、0.14mT组全身骨密度均明显低于空白组（P〈0.05）,0.16mT组、0.18mT组和雌激素组全身骨密度均明显高于去势组（P〈0.05）;第3个月末,各组腰椎骨密度变化趋势与全身骨密度变化基本一致,去势组、0.14mT组股骨骨密度明显低于空白组,但其余各组间比较,差异无统计学意义.结论 频率为50hz,磁感应强度为0.16mT和0.18mT的PEMFs刺激能够促进骨形成,可作为治疗骨质疏松症的参考参数;而频率为50hz,磁感应强度为0.14mT的PEMFs可能具有刺激骨吸收的作用.PEMFs对去势雌性大鼠骨代谢的影响存在较为明显的＂强度窗＂效应.

Objective To investigate the effects of pulsed electromagnetic fields （PEMFs） of different intensities on bone metabolism in ovariectomized rata. Methods Sixty 10-month-old female Sprague-Dawley rats were randomly divided into a normal group, an ovariectomized control group, a 0. 14 mT group, a 0. 16 mT group, a 0.18 mT group and an estrogen group. All rats except those in the normal group were subjected to bilateral ovariectomy. Beginning one week after the operation, the rats in the 0. 14 mT, 0. 16 mT and 0.18 mT groups were treated with PEMFs at 50 Hz, 60 min daily for 90 days, while those in the estrogen group received estrogen instead. During the experiment, the bone mineral density （BMD） of the whole body was observed dynamically, and local BMDs and biochemical indexes were measured after 3 months of treatment. Results Alkaline phosphatase （ALP） activity in the normal group was significantly lower than in the other groups. Tartrate-resistant acidic phosphatase 5b （TRAP5b）activity was elevated significantly, in the control and 0.14 mT groups compared with the normal group. After 2 months of treatment, whole body BMD was reduced significantly in the 0.14 mT group compared to the normal group. After 3 months of treatment, whole body BMD in the ovariectomized controls and the 0.14 mT group was reduced significantly compared to the normal group, but significantly elevated in the 0. 16 mT, 0.18 mT and estrogen groups when compared to the ovariectomized control group. At the end of 3 months of treatment, the trends in lumbar vertebral BMD were similar to those of the whole body BMD, with the femoral BMD in the ovariectomized group and the 0.14 mT group significantly lower than in the normal group, though the differences among the other groups were not statistically significant. Conclusions PEMF treatment at 50 Hz and 0.16 mT or 0.18 mT can promote bone formation. PEMFs at 50 Hz and 0.14 mT might stimulate bone resorption. An intensity-window effect exists in the action of PEMFs on bone metabolism in ovariectomized rats.