title: Cystic fibrosis transmembrane conductance regulator in the endolymphatic sac of the rat.
abstract: OBJECTIVE
  Na(+) and Cl(-) are dominant ions in the endolymphatic fluid in the endolymphatic sac and are important for volume regulation in the endolymphatic sac. An epithelial sodium channel (ENaC) and other Na(+) transporters have been identified in the endolymphatic sac epithelia, and they are involved in the regulation of endolymph. Although the presence of Cl(-) channels in the endolymphatic sac epithelia has been speculated, no Cl(-) channels have been identified. In this study, we confirmed the expression of cystic fibrosis transmembrane conductance regulator (CFTR) in the endolymphatic sac by reverse transcriptase polymerase chain reaction (RT-PCR) and by immunohistochemical staining.
  
  
  METHODS
  Pure mRNA from endolymphatic sac epithelia was prepared using laser capture microdissection (LCM) and examined using RT-PCR. Localization of CFTR and ENaC in the endolymphatic sac was examined using immunohistochemistry.
  
  
  RESULTS
  mRNA of the CFTR was expressed in the endolymphatic sac. Immunohistochemical analysis showed the expression of the CFTR on apical side of the endolymphatic sac epithelia and co-localization with the ENaC.
  
  
  CONCLUSIONS
  RT-PCR and immunohistochemistry were used to identify the expression of CFTR in the endolymphatic sac epithelia, which gives us a clue for understanding Cl(-) transport in the endolymphatic sac. These results suggest a pathway for Cl(-), possibly through interaction with the ENaC, which may regulate the endolymph in the endolymphatic sac.
authors.affiliation: Department of Otolaryngology, Faculty of Medicine, Kagawa University, Japan. Electronic address: aimatsu@med.kagawa-u.ac.jp.
authors.forename: Ai
authors.initials: A
authors.lastname: Matsubara
authors.affiliation: Department of Otolaryngology, Faculty of Medicine, Kagawa University, Japan.
authors.forename: Takenori
authors.initials: T
authors.lastname: Miyashita
authors.affiliation: Department of Otolaryngology, Faculty of Medicine, Kagawa University, Japan.
authors.forename: Ryuhei
authors.initials: R
authors.lastname: Inamoto
authors.affiliation: Department of Otolaryngology, Faculty of Medicine, Kagawa University, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hoshikawa
authors.affiliation: Department of Otolaryngology, Faculty of Medicine, Kagawa University, Japan.
authors.forename: Nozomu
authors.initials: N
authors.lastname: Mori
mesh_terms: D000818:Animals; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics* / Q000378:metabolism; D004712:Endolymphatic Sac / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism*; D053503:Epithelial Sodium Channels / Q000378:metabolism*; D005260:Female; D007150:Immunohistochemistry; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C579654:CFTR protein, rat; D053503:Epithelial Sodium Channels; D012333:RNA, Messenger; D019005:Cystic Fibrosis Transmembrane Conductance Regulator
keywords: Chloride channel; Cystic fibrosis transmembrane conductance regulator (CFTR); Endolymphatic sac; Epithelial sodium channel (ENaC); Immunohistochemistry; RT-PCR