title: [The study of the high sensitivity to noise trauma in the inner ear mimetic aging model].
abstract: OBJECTIVE
  Use the inner ear mimetic aging model which has been established by our research institute, investigate its sensitivity to noise trauma and the possible role of mitochondrial DNA deletions.
  
  
  METHODS
  Thirty-two Wistar rats of 2 months old were randomly divided into four groups. In group A, D-galactose was subcutaneously injected at dose of 150 mg/kg weigh per day for 8 weeks, after that these rats were exposed to 110 dB SPL noise 4 hours each day, for 2 days. Group B were given normal saline (NS) injected at dose of 150 mg/kg weigh per day for 8 weeks,also given noise exposure as that of group A. Group C were give D-galactose without noise exposure. Group D were given normal saline (NS) without noise exposure. The thresholds of auditory brainstem response (ABR) were measured 2 weeks after stopping of noise exposure. And T-SOD and MDA of the inner membranous labyrinthine tissue were measured. Nest polymerase chain reaction (Nest PCR) were used to identify the mtDNA common deletion (CD), and PCR products were sequenced in the meantime.
  
  
  RESULTS
  The elevation of the mean ABR thresholds in group A was higher than that in group B, and the difference had statistic significance (P < 0.01). The reduction of T-SOD in group A was obvious, while the level of MDA was greatly increased. The difference in the levels of T-SOD and MDA between group A and group B had statistic significance (P < 0.01). The detection rate of mtDNA 4834 deletion were as follows: group A 87.5% (7/8); group B 12.5% (1/8); group C 75.0% (1/8); group D 0(0/8).
  
  
  CONCLUSIONS
  The rat in the inner ear mimetic aging model are hypersensitive to noise exposure, and mtDNA4834 deletions in the inner ear may play an important role in it.
authors.affiliation: Department of Otolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.
authors.forename: Li
authors.initials: L
authors.lastname: Xu
authors.forename: Yujuan
authors.initials: Y
authors.lastname: Hu
authors.forename: Weijia
authors.initials: W
authors.lastname: Kong
authors.forename: Hong
authors.initials: H
authors.lastname: Shi
authors.forename: Wei
authors.initials: W
authors.lastname: Peng
authors.forename: Yuan
authors.initials: Y
authors.lastname: Hu
mesh_terms: D000375:Aging; D000818:Animals; D004272:DNA, Mitochondrial / Q000235:genetics; D004195:Disease Models, Animal; D004198:Disease Susceptibility; D007758:Ear, Inner / Q000473:pathology; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D006317:Hearing Loss, Noise-Induced / Q000209:etiology / Q000235:genetics* / Q000473:pathology; D008315:Malondialdehyde / Q000032:analysis; D009622:Noise; D051381:Rats; D017208:Rats, Wistar; D017384:Sequence Deletion; D013482:Superoxide Dismutase / Q000032:analysis
chemical_list: D004272:DNA, Mitochondrial; D008315:Malondialdehyde; D013482:Superoxide Dismutase