柴油机尾气和噪声联合暴露致大鼠听力损失的实验研究

Experimental research on hearing loss of rats co-exposure to diesel engine exhaust and noise

目的探讨柴油机尾气和噪声联合暴露对SD大鼠听力损失的影响。方法24只SD大鼠随机分为4组,每组6只,分别为柴油机尾气暴露组、噪声暴露组、柴油机尾气和噪声联合暴露组、对照组。在暴露结束后第4天,进行听性脑干反应测试。取耳蜗固定后,进行扫描电镜检查和免疫荧光染色,观察耳蜗内外毛细胞形态变化和带状突触损伤的情况。结果各实验组大鼠均出现不同程度的听力损失,听力阈值位移:联合暴露组(43.33±8.31)dB SPL>噪声暴露组(39.25±9.05)dB SPL>柴油机尾气暴露组(32.83±13.22)dB SPL>对照组(27.33±12.90)dB SPL,并且观察到联合暴露组大鼠出现不同程度的耳蜗毛细胞倒伏粘连,带状突触减少。对照组耳蜗带状突触平均荧光表达强度最高,柴油机尾气暴露组、噪声暴露组依次降低,柴油机尾气和噪声联合暴露组最低,对照组与各暴露组耳蜗带状突触平均荧光表达强度差异均有统计学意义(F=94.96,P<0.05)、柴油机尾气暴露组与噪声暴露组、柴油机尾气暴露组与联合暴露组耳蜗带状突触平均荧光表达强度差异均有统计学意义(q=5.484,8.767,P<0.05),噪声暴露组与联合暴露组比较差异无统计学意义(q=3.282,P>0.05)。结论柴油机尾气和噪声联合暴露对听力损失有增强作用,主要表现在耳蜗外毛细胞和耳蜗突触严重受损。

Objective To investigate the effects of co-exposure of diesel engine exhaust and noise on hearing loss of SD rats.Methods Twenty-four SD rats were randomly divided into four groups,including diesel engine exhaust exposure group,noise exposure group,diesel engine exhaust and noise co-exposure group,and control group.On the fourth day after the end of exposure,an auditory brainstem response test was performed.The cochleas of rats were fixed for scanning electron microscopy and immunofluorescence staining to observe the morphological changes of the hair cells inside and outside the cochlea and the damage of the ribbon synapses.Results The rats in all experimental groups showed different degrees of hearing loss and the ranking of hearing thresholds:co-exposure group(43.33±8.31)dB SPL>noise exposure group(39.25±9.05)dB SPL>diesel engine exhaust exposure group(32.83±13.22)dB SPL>control group(27.33±12.90)dB SPL,and different degrees of cochlear hair cell inversion adhesion and reduction of ribbon synapses were observed in the co-exposure group.The mean fluorescence expression intensity of cochlear ribbon synapses was the highest in control group,decreased in diesel exhaust exposure group and noise exposure group,and the lowest in diesel exhaust and noise combined exposure group.The difference in mean fluorescence expression intensity of cochlear ribbon synapses between the control group and each exposure group was statistically significant(F=94.96,P<0.05),and the difference between the diesel exhaust exposure group and the noise exposure group,and between the diesel exhaust exposure group and the co-exposure group were all statistically significan(t q=5.484,8.767,P<0.05),while there was no significant difference in the noise exposure group compared to the co-exposure group(q=3.282,P>0.05).Conclusion Co-exposure of diesel engine exhaust and noise exposure had an enhancing effect on hearing loss of rats,and showed severe degree of the outer cochlear hair cells damage.