title: Decreased urinary calbindin 1 levels in proteinuric rats and humans with distal nephron segment injuries.
abstract: BACKGROUND
  Several proteins have been proposed as new urinary biomarkers of kidney injuries, but they are not always capable of identifying the kidney nephron segment that has been injured. Since calbindin 1 protein is exclusively localized in the kidney distal nephron segment, it is presumed that its expression is altered during distal nephron segment injuries, resulting in changes in its urinary excretion.
  
  
  METHODS
  Calbindin 1 expression in normal rat kidneys was compared with that in the kidneys of rats that had suffered distal nephron segment injuries (unilateral ureteral obstruction [UUO] or anti-glomerular basement membrane glomerulonephritis [anti-GBM GN]) using immunohistochemical examinations and real-time polymerase chain reaction. The urinary calbindin 1 protein concentration of normal rats was also compared with that of anti-GBM GN rats and of cisplatin nephropathy rats using Western blotting. We also compared the kidney and urinary calbindin 1 protein concentrations of normal human subjects with those of proteinuric patients [immunoglobulin (Ig)A nephropathy; IgAN] with distal nephron segment injuries.
  
  
  RESULTS
  Calbindin 1 mRNA expression in the renal cortices and calbindin 1 protein expression in the kidney distal nephron segments were decreased in the UUO and anti-GBM GN rat kidneys. The urinary calbindin 1 protein levels of the anti-GBM GN rats were also markedly decreased, whereas those of the cisplatin nephropathy rats were slightly decreased. The human IgAN patients displayed decreased renal calbindin 1 protein expression in their dilated distal tubules, and some patients displayed decreased urinary calbindin 1 levels.
  
  
  CONCLUSIONS
  Since it has been demonstrated that decreased urinary calbindin 1 levels are indicative of decreased calbindin 1 kidney expression due to distal nephron segment injuries, calbindin 1 might be a useful urinary biomarker for identifying distal nephron segment injuries.
authors.affiliation: Institute for Clinical Research, Niigata National Hospital, 3-52 Akasaka-cho, Kashiwazaki, 945-8585, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Iida
authors.forename: Hidehiko
authors.initials: H
authors.lastname: Fujinaka
authors.forename: Bo
authors.initials: B
authors.lastname: Xu
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Sameh
authors.initials: S
authors.lastname: Magdeldin
authors.forename: Masaaki
authors.initials: M
authors.lastname: Nameta
authors.forename: Zan
authors.initials: Z
authors.lastname: Liu
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Yoshida
authors.forename: Eishin
authors.initials: E
authors.lastname: Yaoita
authors.forename: Shuichi
authors.initials: S
authors.lastname: Tomizawa
authors.forename: Akihiko
authors.initials: A
authors.lastname: Saito
authors.forename: Tadashi
authors.initials: T
authors.lastname: Yamamoto
mesh_terms: D000293:Adolescent; D000818:Animals; D015415:Biomarkers / Q000378:metabolism / Q000652:urine; D064092:Calbindin 1 / Q000378:metabolism / Q000652:urine*; D002648:Child; D004195:Disease Models, Animal; D005921:Glomerulonephritis / Q000652:urine*; D005922:Glomerulonephritis, IGA / Q000652:urine*; D006801:Humans; D007668:Kidney / Q000378:metabolism / Q000473:pathology; D007686:Kidney Tubules, Distal / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D009399:Nephrons / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D011507:Proteinuria / Q000652:urine*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011921:Rats, Inbred WKY; D014517:Ureteral Obstruction / Q000652:urine*
chemical_list: D015415:Biomarkers; C576498:CALB1 protein, human; C576500:Calb1 protein, rat; D064092:Calbindin 1; D012333:RNA, Messenger