title: Comparison of the quantity of cochlear melanin in young and old C57BL/6 mice.
abstract: OBJECTIVE
  To elucidate the functional relationship between cochlear melanin and aging.
  
  
  METHODS
  Melanin has been described in the cochlear labyrinth and has been suggested to protect the cochlea from various types of trauma. The quantity of melanin has been shown to change with aging in several organs; however, to our knowledge, aging changes in the cochlea have not been documented. Therefore, we chemically quantified cochlear eumelanin and pheomelanin contents and compared these in young and old C57BL/6 mice using high-performance liquid chromatography. Because melanin deposits in the cochlea present most extensively in the stria vascularis, we morphologically examined the stria using transmission electron microscopy.
  
  
  METHODS
  Cochleae from an inbred strain of C57BL/6 male and female mice; 6 at the age of 10 weeks and 5 at the age of 100 weeks were studied.
  
  
  RESULTS
  The quantities of cochlear eumelanin and pheomelanin were 421 and 480 ng per cochlea in young mice, and 2060 and 765 ng per cochlea in old mice, respectively. Under transmission electron microscopy, the number of pigmented granules seemed to be greater in older mice compared with younger mice, especially in marginal cells.
  
  
  CONCLUSIONS
  To our knowledge, our findings are the first quantitative evidence to show an age-related overexpression of cochlear melanin and an alteration in the proportion of eumelanin and pheomelanin with aging, suggesting a possible otoprotective function of eumelanin against age-related cochlear deterioration.
authors.affiliation: Department of Otorhinolaryngology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Hayashi
authors.forename: Michihiko
authors.initials: M
authors.lastname: Sone
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Schachern
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Wakamatsu
authors.forename: Michael M
authors.initials: MM
authors.lastname: Paparella
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Nakashima
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D003051:Cochlea / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D005260:Female; D008297:Male; D008543:Melanins / Q000032:analysis* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D046529:Microscopy, Electron, Transmission; D013316:Stria Vascularis / Q000737:chemistry* / Q000648:ultrastructure
chemical_list: D008543:Melanins; C018362:pheomelanin; C041877:eumelanin