被动吸烟影响仔鼠小脑皮质神经生长因子含量及牛磺酸的干预作用

背景:被动吸烟致对胚胎神经系统发育影响的报道比较少见,并缺乏有效的防治措施。我们以往实验证明,被动吸烟可致仔鼠海马组织神经生长因子含量减少,学习能力下降。小脑皮质也是胚胎期神经生长因子水平较高的部位之一,被动吸烟也可能降低小脑皮质神经生长因子的含量。牛磺酸在哺乳类动物的脑内含量丰富,神经元和神经胶质细胞可能通过选择性储存和释放牛磺酸,以维持脑组织的正常活动,牛磺酸的合成和摄入受阻可能导致其功能异常。因此推测胚体内一定水平的牛磺酸与神经生长因子含量具有相关性,而小脑皮质神经生长因子含量的减少可能是仔鼠脑损伤的原因之一,故设计此实验。目的:探索被动吸烟对仔鼠所致脑损害机制及牛磺酸的干预作用。设计:随机对照动物实验。单位:山西医科大学汾阳学院。材料:实验于2001-03/2001-12在山西医科大学汾阳学院中心实验室进行。选Wistar雌性大鼠21只,体质量150～210g,采用编号随机分组方法分为3组,每组7只:被动吸烟组,被动吸烟 牛磺酸组,正常对照组。3组大鼠均于受孕的第2天起进行处理至自然分娩。被动吸烟组给予连续实验性吸烟,每日吸烟前用生理盐水0.65mL/只灌胃;被动吸烟 牛磺酸组于每日吸烟前用牛磺酸500mg/kg灌胃;正常对照组不予吸烟,每日用生理盐水0.65mL/只灌胃。方法:各组孕鼠分娩的仔鼠称量体质量后断头法处死,分离出脑并称重,在沸生理盐水中煮5min。再分离出小脑,用免疫放射测定法测神经生长因子含量。以小脑皮质神经生长因子蛋白变化为指标观察被动吸烟及牛磺酸对其的影响。主要观察指标:各组仔鼠体质量、脑质量和小脑神经生长因子蛋白的比较。结果:21只孕鼠的147只仔鼠检测数据进入结果分析。被动吸烟组仔鼠的体质量、脑质量和小脑神经生长因子蛋白水平分别与正常对照组和被动吸烟 牛磺酸组比较均显著降低(P<0.001);被动吸烟 牛磺酸组仔鼠的3项指标与正常对照组比较差异无显著性意义(P>0.05)。结论:被动吸烟可能是导致仔鼠小脑皮质神经生长因子水平下降的因素;牛磺酸可能对被动吸烟所致仔鼠脑损害具有保护作用。

Effect of passive smoking on content of nerve growth factor in cerebellar cortex of fetal rats and the interventional effect of taurine

BACKGROUND: Reported about passive smoking on development of nervous system are rare and it is lack of preventive and therapeutic measures.Previous animal experiments proved that passive smoking at pregrancy could decrease content of Nerve growth factor (NGF) in hippocampal tissue and eliminate abilities of learning of fetal rats. Cerebellar cortex contain high levels of NGF at embryonic phase. Passive smoking decrease content of NGF in cerebellar cortex. Brain of mammalis animal is full of taurine which is released by neuron and neuroglia cell to maintain normal activities in cerebral tissue. Inhibitory synthesis and ingestion of taurine can cause disfunction.Therefore, a certain level of taurine is possibly correlated with expression of NGF gene in embryoids. However, the decrease of NGF content in cerebellar cortex may be one of factors for brain injury of fetal rats.OBJECTIVE: To investigate the mechanism of brain injury induced by passive smoking in fetal rats and the interventional effect of taurine.DESIGN: Randomized controlled animal study.SETTING: Fenyang College of Shanxi Medical University.MATERIALS:Twenty-one 2-month-old female Wistar rats,weighing 150-210 g, were randomly divided into 3 group with 7 rats in each group,including passive smoking group, passive smoking+taurine group and normal control group. All rats in the three groups were treated till naturalpartrition from the second day of cyesis. Rats in the passive smoking group were suffered from successively experimental smoking after intragastrical administration with 0.65 mL/ampoule saline; rats in the passive smoking+taurine group were intragastrically administrated with 500 mg/kg taurine before smoking rats in the normal contrl group did not smoke and were intragastrically administrated with 0.65 mL/ampoule saline every day.METHODS: Newborn rats were weighed and then their heads were cut off. Rapidly, brains were separated,weighed,boiled in boiling saline for 5 minuters. Then, cerebellum was separated. Content of NGF in cerebellar tissue of fetal rats were measured with immune-radio technique. Changes of NGF protein in cerebellar cortex were regarded as the indexes to analyze the effect of passive smoking and taunine on them.MAIN OUTCOME MEASURES: Comparisons of body mass, cerebral mass and the contents of NGF protein.RESULTS: A total of 147 fetal rats were involved in the final analysis,Levels of body mass, cerebral mass and the contents of NGF protein were markedly lower in passive smoking group than those in normal control group and passive smoking + taurine group (P ＜ 0.001). There was no significant difference of the three indexes between passive smoking + taurine group and normal control group (P ＞ 0.05).CONCLUSION: Passive smoking is a possible factor for decreasing level of NGF in cerebellar cortex of fetal rats, and taurine may protect brain injury induced by passive smoking.