雌激素对模拟航天环境听觉器官的保护作用

Protective Effects of Estrogen on Cochlea during Mid-Long Term Simulated Manned Spacecraft Environment

目的探讨模拟失重及飞船舱内噪声复合因素对大鼠听觉电生理与超微结构的影响,及雌激素对上述复合因素损伤的保护作用。方法 32只SD大鼠随机分为A、B、C3组,其中A组(失重+噪声组)12只,B组(雌激素+失重+噪声组)12只,C组(对照组)8只。A组、B组动物均粘尾悬吊模拟失重,同时模拟飞船舱内噪声暴露8周,B组动物在此基础上每周两次肌注苯甲酸雌二醇0.02mg/只,首剂加倍,至暴露结束。分别于暴露前、暴露后3天、1周、2周、4周、8周检测其双耳听性脑干反应阈值(ABR)。并于暴露结束后取耳蜗标本进行电镜扫描。结果组内对照,A组SD大鼠在暴露3天直至暴露8周后ABR阈值均较暴露前明显增高(P<0.01);B组SD大鼠在暴露3天直至暴露8周后ABR阈值均较暴露前亦有所增高(P<0.05);C组SD大鼠在暴露2周较暴露1周ABR阈值有所提高(P<0.05),其他时间点增高不显著。组间对照,A组大鼠在暴露3天至暴露8周均较C组大鼠听力显著提高(P<0.01);B组大鼠在暴露3天至暴露8周较C组听力无明显提高(P>0.05);A组大鼠至暴露1周时较B组大鼠听力升高不明显,在以后时间点均较B组大鼠听力明显升高(P<0.05)。扫描电镜显示A组损伤最重,B组损伤次之,C组未见异常。结论失重和噪声复合因素可造成SD大鼠听觉电生理及内耳毛细胞的损伤,雌激素对失重和噪声复合因素下的听功能损伤具有一定保护作用。

Objective To study the effects of compound factors of weightlessness and noise in spaceship on rat hearing and cochlear morphology, as well as protection against auditory damage by estrogen. Methods Thirty two SD rats were randomly divided into groups A and B （n=12 each） and group C （n=8） Animals in groups A and B were subjected to glued tail suspension to simulate weightlessness, and exposed to simulated spaceship noise for 8 weeks. Additionally, animals in group B were injected with 0.02 mg benzoate twice a week （first dose = 0.04 mg） until the end of the experiment. Auditory brainstem response （ABR） thresholds were tested bilaterally before and at 3 days, 1 week, 2 weeks, 4 weeks and 8 weeks after noise exposure. The cochlea was harvested and processed for scanning electron microscopy （SEM） studies at the end. Results ABR thresholds were significantly higher in group A than other groups （P 〈 0.01）. The longer the exposure, the higher the thresholds. ABR thresholds in group B were also increased along with noise exposure （P 〈 0.05）. ABR thresholds in group C increased along with noise exposure from week 1 to week 2 （P 〈 0.05）, but not significantly at other time points （P 〉 0.05）. ABR thresholds in group A were higher than in group C at all times （P 〈 0.01）. ABR thresholds in group B were not significantly different than in group C from day 3 to 8 weeks. （P 〉 0.05）. ABR thresholds in group A were not significant- ly different from group B during the 1st week, but higher than group B at other time points （P 〈 0.05）. SEM showed the most severe cochlear damage in group A, followed by group B. Only mild cochlear change was observed in group C. Con- clusions Simulated weightlessness and noise exposure can cause damage to hearing and changes of cochlear morphology in SD rats. Estrogen appears to protect against such damages.