模拟失重和噪声对大鼠听功能及耳蜗Corti 器损伤的协同作用

摘要

目的：探讨模拟失重和噪声对大鼠听功能及耳蜗Corti器损伤的协同作用。方法48只大鼠随机分为空白组、失重组、噪声组和失重＋噪声组，每组12只。失重组以Morey －Holton法模拟失重环境，噪声组暴露的噪声环境为模拟航天载人飞船内复合噪声，包括72±2 dB SPL的持续稳态噪声和160 dB SPL的脉冲噪声，失重＋噪声组则同时暴露于上述失重及噪声环境中，空白组常规饲养，不做任何处理。分别于暴露1周和2周后，每组随机选出6只大鼠行ABR阈值检测后取材行 HE染色、免疫荧光（DAPI）染色及扫描电镜观察耳蜗的形态学变化。结果暴露2周后大鼠ABR阈值较暴露1周时升高，失重＋噪声组ABR阈值最高（ P＜0．01），其次为噪声组。HE染色示暴露1周和2周后除空白组外各组大鼠耳蜗Corti器均有不同程度的损伤，失重＋噪声组最严重。免疫荧光染色示暴露1周后大鼠耳蜗毛细胞死亡方式以肿胀坏死为主，失重＋噪声组最严重（肿胀率10％），其次为噪声组（肿胀率3．33％）；暴露2周后大鼠耳蜗外毛细胞以核缺失为主，失重＋噪声组缺失率最高（缺失率13．6％），其次为噪声组（缺失率12．7％），失重组毛细胞缺失以内毛细胞为主。扫描电镜示，失重＋噪声组毛细胞静纤毛损伤最严重，其次为噪声组，再次为失重组。结论模拟失重和噪声环境对大鼠听功能的影响有协同作用，且这种协同作用对耳蜗Corti器有显著的损伤作用。%Objective To investigate the synergistic effects of simulated microgravity and noise on the audito‐ry functions and corti organs in rats .Methods A total of 48 healthy rats were randomly divided into 4 groups (n=12):control group (Group A) ,microgravity only group (Group B) ,noise only group (Group C) and microgravity+noise group (Group D) .The microgravity environment was simulated by suspending the posterior limb using Morey-Holton method .The noise exposure was the simulation of the noise environment in spaceship including steady -state noise (72 ± 2) dB SPL and impulse noise up to 160 dB SPL .The control group was kept in normal conditions without any exposure .Auditory brainstem responses (ABRs) ,HE stainings ,immunofluorescence stainings and scanning electron microscopes (SEMs) were tested after 1week and 2 weeks exposure respectively (n=6) .Results The average of ABR threshold shifts of 2 weeks exposure were higher than those of 1 week in each group .Group D showed the highest ABRs (P<0 .01) .The HE stainings showed different degrees of injury in corti organs in all experimental groups ;which Group D being the most serious ,followed by Group C .The results of immunefluorescence in hair cells showed that swelling necrosis was the main damage of cochlear hair cell after 1 week's exposure .The swelling rate of Group D was the highest ,followed by Group C .Nucleus missing in hair cells was observed after 2 weeks'exposure . Group D had the highest missing rate and the main missing of Group B happened in the inner hair cells .SEM showed that the most serious damage of stereociliums in Group D ,followed by Group C ,then Group B .Conclusion The synergistic effects of simulated microgravity and noise lead to significant damage of the auditory function and cochlea Corti organs in rat .