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

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 technology. 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
Free radicals in the cochlea increase evidently and have a concentration-time rule after acute acoustic trauma. The ESR method can be used to examine the content of free radicals in cochlea for its direct, objective and sensitive characters.