电子自旋共振技术观察急性声损伤后耳蜗自由基改变

Using ESR technology observe the change of free radicals in cochlea after acute acoustic trauma

目的:应用电子顺磁自旋共振(ESR)技术观察急性声损伤后豚鼠耳蜗自由基的变化规律。方法:将正常白毛红目豚鼠48只分为3组:A组(对照组)取6只豚鼠不给予噪声刺激,分别在检测听功能后测定自由基和硝酸银染色。B组21只豚鼠在(125±1)dB SPL稳态噪声暴露2 h后分别于即刻、2 h、6 h、12 h、24 h、48 h、72 h施行ABR测试和ESR检测耳蜗自由基。检测方法为断头后快速取出耳蜗,液氮速冻。样品处理后放入ESR系统谐振腔中检测自由基含量。C组21只豚鼠在噪声暴露后于上述时间点检测听觉功能并取基膜行硝酸银染色观察Corti器毛细胞形态改变。结果:①正常豚鼠耳蜗中有少量自由基存在,其相对自由基值为(21.68±1.27)。噪声暴露后即刻取样组自由基值明显升高,在暴露后2 h达峰值(147.01±4.95)dB SPL,此后逐渐下降,至72 h恢复至接近正常水平(53.12±2.57)dB SPL;②在125 dB SPL的急性噪声暴露后,豚鼠的听阈明显提高,至6 h达到峰值(73.89±2.41)dB SPL,直至72 h仍未恢复到暴露前正常水平(50.28±1.48)dB SPL;③急性声损伤后形态学改变表现为外毛细胞纤毛紊乱、排列不规则,部分区域可见毛细胞缺失。结论:①急性噪声暴露后,豚鼠耳蜗内自由基水平明显增高,并在2 h达峰值;②应用ESR技术检测耳蜗组织中自由基含量的方法具有直接、客观和灵敏的特点,ESR技术可用于某些内耳急性损伤动物模型的实验观察。

Objective：To observe the changes of free radicals in the cochlea of guinea pigs after noise exposure directly using electron spin resonance（ESR） technology.Method：Forty-two guinea pigs as experimental group were given（125±1）dB SPL noise exposure for 2 hours,and then investigated auditory function immediately,at 2,6,12,24,48 and 72 hour.After ABR examinations,21 animals decollated and extracted cochlea immediately and then placed the cochleas to liquid nitrogen for deep freezing and measuring free radicals using ESR techonology.Another 21 animals observed hair cells morphology by AgNO3 staining.Meantime,6 animals without noise exposure were served as negative control group.Result：A few free radicals were detected in the cochlea at control group and the relative value of free radicals were（21.68±1.27）dB SPL.After noise exposure,the relative value of free radicals increased obviously and achieved to the max of（147.01±4.95）dB SPL at 2 h and gradually decreased near the normal level.Conclusion：①Free radicals in the cochlea increase evidently and have a concentration-time rule after acute acoustic trauma.②The ESR method can be used to examine the content of free radicals in cochlea for its direct,objective and sensitive characters.