Objective To explore the underlying mechanism of respiratory syncytial virus-related asthma .Methods Totally 30 sprague-dawley rats were randomly divided into control group ,respiratory syncytial virus (RSV) group ,and anti-NGF group ,with 10 in each group .RSV infection model was established by nasal drip once a week .In anti-NGF antibody intervention group ,each rat was given intraperitoneal injection of anti-NGF for 3 h before identical RSV infection .transmission electron microscopy(TEM) were performed to observe the ultramicro-structure changes in adrenal medullary cell .The concentrations of adrenaline and NGF in serum were measured by ELISA .The NGF expression was assayed by immunohistochemistry .The expression difference of neurofilament protein mRNA was detected by RT-PCR .Results (1) Electron microscope showed ,medullary cells riched in mitochondria ,Chro-maffin granule concentration decreased obviously ,and membrane could saw clubbing phenomenon of neurite outgrowth clearly in RSV infection group .Meanwhile ,NGF expression was significantly increased in RSV infection group .(2) ELISA results showed that the concentrations of NGF in the RSV group was significantly increased compared with control group and anti-NGF group(P<0 .05) ,while the concentrations of NGF showed no difference between control group and anti-NGF group(P> 0 .05) .Compared with control group ,the adrenaline concentration of RSV group and anti-NGF group was significantly decreased(P<0 .01) ,and the adrenaline concentration of RSV group was significantly decreased compared with anti-NGF antibody group(P<0 .05) .(3) NF-LmRNA expression was significantly increased in RSV group .However ,compared with control group ,the NF-LmRNA expression was significantly decreased in anti-NGF group .(4) RT-PCR results show that ,Compared with control group ,adrenal medullary cells NF-LmRNA expression of RSV group and the anti-NGF group was significantly increased .Compared with RSV group ,NF-LmRNA adrenal medulla cells in Anti-NGF group was significantly decreased .Conclusion RSV infection may induce the adrenal medullary cell differentiation to nerve cell by over-expressed NGF ,and result in the decrease of adrenaline in serum to involve in asthma progression .%目的：探讨呼吸道合胞病毒（RSV）感染大鼠相关性哮喘的可能相关机制。方法 SD大鼠30只，随机分为对照组、RSV组和抗神经生长因子（NGF）组，每组10只。RSV组采用每周1次RSV滴鼻法复制RSV感染模型。抗NGF组先腹膜腔内注射山羊抗大鼠β-NGF抗体，3 h后按照RSV组相同的方法进行RSV感染。电镜观察肾上腺髓质细胞超微结构变化，ELISA检测血清NGF和肾上腺素浓度变化，免疫组织化学检测肾上腺髓质细胞NGF表达变化，RT-PCR检测肾上腺髓质细胞NF-L mR-NA表达差异。结果（1）电镜下 RSV组髓质细胞线粒体丰富，嗜铬颗粒浓度明显降低，细胞膜可见明显杵状突起生长现象。（2）ELISA结果显示，RSV组大鼠血清NGF浓度明显高于对照组和抗NGF组（P＜0．05），而对照组和抗NGF组大鼠血清NGF浓度差异无统计学意义（P＞0．05）。与对照组相比，RSV组和抗NGF组血清肾上腺素浓度明显下降（P＜0．01）；与抗NGF组相比，RSV组血清肾上腺素浓度明显下降（P＜0．05）。（3）免疫组织化学显示，与对照组和抗NGF组相比，RSV组肾上腺髓质细胞NGF阳性表达明显增强；与对照组相比，抗NGF组肾上腺髓质细胞 NGF阳性表达也明显增强。（4）RT-PCR结果显示，与对照组相比，RSV组和抗NGF组肾上腺髓质细胞NF-L mRNA表达明显增强；与RSV组相比，抗NGF组肾上腺髓质细胞NF-L mR-NA表达明显减弱。结论 RSV感染相关性哮喘的发生可能与NGF诱导肾上腺髓质细胞向神经元细胞转化导致血清中肾上腺素浓度下降有关。
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