内皮素在噪声性内耳损伤过程中的作用

目的研究噪声性内耳损伤过程中耳蜗微循环的病理变化以及内皮素(endothelin，ET)在这一病理过程中的作用及意义。方法30只大鼠按电脑产生随机数字法分为5组：对照组、噪声暴露(115dB白噪声每天8h)1、4、8和15d组。分别用扫描电镜观察毛细胞的形态，血管纹铺片观察耳蜗微循环的状态，放射免疫方法检测血浆ET含量，免疫组化染色观察ET-1、ETA、ETB的分布。结果噪声4、8、15d组出现了血管纹明显缺血，外毛细胞形态异常。血浆ET于4d组出现暂时性升高。ET-1于耳蜗组织中有广泛的阳性表达，噪声暴露前后差异无统计学意义；ETA主要分布于血管纹中间细胞与微血管壁周围的细胞，对照组与1d组表达呈弱阳性( )，噪声4、8、15d组表达呈强阳性( )。ETB主要分布于血管纹毛细血管内皮细胞，其变化趋势与ETA相似。结论噪声性内耳损伤过程中出现了明显的耳蜗微循环障碍，同时大鼠耳蜗组织的ET系统活性增高，二者在时间上有明显的一致性。推测噪声所致的耳蜗微循环障碍过程中ET起了重要的介导作用。

Contributions of endothelin in the process of the noise-induced injury of inner ear

OBJECTIVE: To study the pathological alteration of the cochlear microcirculation and the role of endothelin (ET) in the process of the noise-induced injury of inner ear. METHODS: Thirty rats were randomly divided into five groups: control group and 1, 4, 8, 15 d noise exposure groups (115 dB, white noise, 8 h daily). The cilium of hair cell was observed by scanning electron microscope, the cochlear microcirculation was determined by stretched preparation of the stria vascularis. The level of ET in plasm was measured through radio-immunity. The distribution of ET-1, ETA, ETB, in cochlea were detected through immunohistochemistry staining. RESULTS: In the 4, 8, 15 d group, severe ischemia appeared on the capillary of stria vascularis and the cilium of hair cell displayed significantly disorder. The level of ET in plasm rose temporarily in the 4 d group. ET-1 activity distributed widely in the rat cochlea, there was no significant difference between the control group and the noise exposure groups. ETA expressed in the plasm of the intermediate cells and the capillary walls in the stria vascularis. The control group and the 1 d group showed weak positive staining, while the 4, 8, 15 d groups showed strong positive. The ETB, activity distributed on the endothelial cells of the capillary of stria vascularis and the alteration of the staining intensity was similar to the manifestation of ETA. CONCLUSIONS: Severe disturbance of the cochlear circulation occured during the course of the noise injury to the inner ear. At the same time, the activity of the ET system of the cochlea stepped up significantly. It coincided with the ischemia of the stria vascularis. These findings suggest that ET may play an important role in the process of the cochlear microcirculation disorder caused by noise.