The Study Of The High Sensitivity To Noise Trauma In The Inner Ear Mimetic Aging Model

PART 1 The high sensitivity to the niose trauma in the inner ear mimetic aging modelObjective: To establish the inner ear mimetic aging model and investigate its high sensitivity to niose trauma. Methods thirty-two wistar rats of 2 months old were divided into four groups in random principle: for group A, D-galactose was subcutaneously injected at dose of 150mg/kg weigh per day for 8 weeks, after that these rats were exposed to 110 dBSPL noise for 4 hours each day continuously for 2 days. Group B were given nomal saline(NS)injected at dose of 150mg/kg weigh per day for 8 weeks ,also given noise exposing as that of group A. Group C were given D-galactose , not exposed to the noise. Group D were given nomal saline(NS), not exposed to the noise. The thresholds of auditory brainstem (ABR) were measured after 2 week of stopping the noise exposing. And T-SOD and MDA of the inner membranous labyrinthine tissue were measured. Results The elevation of the mean ABR thresholds after noise exposing between group A and group B have statistic significance. (p<0.01) The differences of levels of T-SOD and MDA between any two groups also have statistic significance(P<0.01). Conclusion D-galactose may induce hypersensitivity of the rats to noise trauma.PART 2 The role of mitochondrial DNA deletions in the high sensitivity of the rat to noise traumaObjective To investigate the possible role of mitochondrial DNA deletions in the high sensitivity of the rat to noise trauma. Methods The inner ear membranous labyrinthine tissues of rats described in dissertation part 1 were harvested and DNA were isolated. Nest polymerase chain reaction(Nest PCR) were used to identify the mtDNA common deletion (CD), PCR products were sequenced in the meantime. Results The detection rate of mtDNA4834 deletion are as follow: group A(7/8); group B (1/8); group C(6/8); group D (0/8)。Conclusion D-galactose can induce mtDNA 4834deletions in the inner ear which may play an important role in the hypersensitivity to noise induced hearing loss.