title: Increased activity of mitochondrial respiratory chain complex in noise-damaged rat cochlea.
abstract: CONCLUSIONS
  Functional changes of mitochondrial respiratory chain (MRC) and hearing threshold shifts were observed after noise exposure and the pattern was different depending on the extent of the noise damage.
  
  
  OBJECTIVE
  The aim of this study was to reveal any functional changes of the MRC enzyme in outer hair cells after noise damage.
  
  
  METHODS
  Sprague-Dawley rats were used and divided into three groups including normal control group and noise exposure for 1 h and 5 h. White band noise was used with 120 dB SPL. We measured hearing threshold and activity of succinate dehydrogenase (SDH) before noise exposure, and immediately and 1, 3, 7, and 14 days after noise exposure in each group. Immunostaining using monoclonal anti-MRC complex V subunit α was performed. Transmission electron microscopy (TEM) was carried out.
  
  
  RESULTS
  The hearing threshold level changed depending on the exposure time in both the noise-exposed groups. In the 1 h group, hearing was improved after 1 day, and in the 5 h group, hearing was measured after 7 days. Changes in SDH activity were observed at the third day in the 1 h group and at the seventh day in the 5 h group. The expression level of MRC complex V was increased after noise exposure. TEM showed mitochondrial damage.
authors.affiliation: Department of Otorhinolaryngology, Boramae Medical Center, Seoul Metropolitan Government-Seoul National University, Seoul, Korea. drpark@snu.ac.kr
authors.forename: Min-Hyun
authors.initials: MH
authors.lastname: Park
authors.forename: Ho Sun
authors.initials: HS
authors.lastname: Lee
authors.forename: Jae Jin
authors.initials: JJ
authors.lastname: Song
authors.forename: Sun O
authors.initials: SO
authors.lastname: Chang
authors.forename: Seung-Ha
authors.initials: SH
authors.lastname: Oh
mesh_terms: D000818:Animals; D001309:Auditory Threshold; D015153:Blotting, Western; D004195:Disease Models, Animal; D004579:Electron Transport / Q000502:physiology; D016057:Evoked Potentials, Auditory, Brain Stem; D006198:Hair Cells, Auditory / Q000378:metabolism* / Q000648:ultrastructure; D006317:Hearing Loss, Noise-Induced / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D007150:Immunohistochemistry; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley