title: Synthesis of atrial natriuretic peptide in the rabbit inner ear.
abstract: OBJECTIVE
  Atrial natriuretic peptide (ANP) exhibits natriuretic, diuretic, and vasorelaxant activity, maintaining fluid and electrolyte homeostasis. Although ANP is mainly synthesized and secreted in/from atrium, ANP has been found in various tissues including the rat inner ear. The aim of this study was to identify the synthesis of ANP in lateral cochlear wall tissues and the presence of ANP in perilymph using rabbits.
  
  
  METHODS
  In vivo study using a rabbit model.
  
  
  METHODS
  Expression of ANP in the rabbit inner ear tissue and the presence of perilymph were examined by radioimmunoassay and polymerase chain reaction using an ANP polyclonal antibody and rat ANP primers, respectively. Characteristics of ANP and pro-ANP present in the inner ear were also evaluated by high-performance liquid chromatography (HPLC), comparing to rat cardiac ANP and pro-ANP.
  
  
  RESULTS
  Immunoreactive ANP (ir-ANP) was found in the perilymph and lateral cochlear wall tissue of rabbits. The levels of ir-ANP in the perilymph were 5 to 16 ng/mL. Elusion profiles of HPLC showed two main peaks that were exactly matched with rat cardiac ANP and pro-ANP. Expression of ANP mRNA was also detected.
  
  
  CONCLUSIONS
  Our findings suggest that ANP and its precursor protein are synthesized in the ear tissues and secreted to perilymph. This hormone may play a role in control of water and/or ion homeostasis of the fluids in the ear that are responsible for normal hearing.
authors.affiliation: Department of Otolaryngology, Research Institute of Clinical Medicine, Chonbuk National University and Chonbuk National University Hospital, Jeon-ju, Republic of Korea. yjyoon@chonbuk.ac.kr
authors.forename: Yong Joo
authors.initials: YJ
authors.lastname: Yoon
authors.forename: Eun Jung
authors.initials: EJ
authors.lastname: Lee
authors.forename: Suhn Hee
authors.initials: SH
authors.lastname: Kim
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000096:biosynthesis*; D007758:Ear, Inner / Q000378:metabolism*; D008297:Male; D011817:Rabbits
chemical_list: D009320:Atrial Natriuretic Factor