title: Daily variance of urinary excretion of AQP2 determined by sandwich ELISA method.
abstract: BACKGROUND
  Urinary excretion of aquaporin 2 (AQP2) is a useful marker of kidney collecting duct function. A specific and convenient method to measure AQP2 in human urine would help to treat water balance disorders. It is unknown whether urinary excretion of AQP2 shows any daily variance.
  
  
  METHODS
  A sandwich enzyme-linked immunosorbent assay (ELISA) method for AQP2 was established using two different kinds of antibodies, and its sensitivity and specificity were examined. Daily variance of urinary excretion of AQP2 and responses to acute water load were examined.
  
  
  RESULTS
  The established ELISA specifically detected urine AQP2 with high sensitivity (detected as low as 0.34 pmol/mL). Urinary excretion of AQP2 did not show daily variance between 9 a.m. and 9 p.m. in healthy subjects.
  
  
  CONCLUSIONS
  The developed ELISA method using two different antibodies is convenient and highly sensitive, and could be useful in clinical practice. Urinary excretion of AQP2 is relatively constant from morning to night, and spot urine sampling at any time during this time period does not affect the results.
authors.affiliation: Department of Nephrology, Tokyo Medical and Dental University, Tokyo, Japan. ssasaki.kid@tmd.ac.jp
authors.forename: Sei
authors.initials: S
authors.lastname: Sasaki
authors.forename: Yasukazu
authors.initials: Y
authors.lastname: Ohmoto
authors.forename: Toyoki
authors.initials: T
authors.lastname: Mori
authors.forename: Fusako
authors.initials: F
authors.lastname: Iwata
authors.forename: Masahiro
authors.initials: M
authors.lastname: Muraguchi
mesh_terms: D051399:Aquaporin 2 / Q000652:urine*; D002940:Circadian Rhythm; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D006801:Humans; D007685:Kidney Tubules, Collecting / Q000502:physiology; D012680:Sensitivity and Specificity
chemical_list: D051399:Aquaporin 2