title: Developmental characteristics of urinary coproporphyrin I/(I + III) ratio.
abstract: BACKGROUND
  The ratio of urinary coproporphyrin (UCP) I to total urinary coproporphyrin I and III [UCP {I/(I + III)]] serves as a biomarker of the ATP-binding cassette, sub-family C, member 2 (ABCC2) function. The aim of this study was to clarify the characteristics of the developmental pattern of UCP [I/(I + III)] in order to estimate ABCC2 function in children, especially in the neonatal period, by measuring it throughout the entirety of childhood.
  
  
  METHODS
  Measurement of UCP [I/(I + III)] was done high-performance liquid chromatography, using urine samples collected from children from 1 day to 15 years old, involving one sample per child. Urine samples from children with liver and kidney disease and urinary tract infection were excluded.
  
  
  RESULTS
  UCP [I/(I + III)] varied widely in infants younger than 6 months old, and was ≥0.3 in 80% of the infants. In contrast, it decreased to <0.30, the lowest, at 1-2 years old. In the 0-6-month-old group, no significant correlation was noted between postnatal age and UCP [I/(I + III)], but a moderate inverse correlation was noted between corrected gestational age and UCP [I/(I + III)].
  
  
  CONCLUSIONS
  UCP [I/(I + III)] is inversely correlated with corrected gestational age and is lowest at 1-2 years old. This suggests that ABCC2 activity is correlated with corrected gestational age and is highest at 1-2 years old.
authors.affiliation: Department of Pediatrics, Faculty of Medicine, Kagawa University, Kagawa, Japan. kunikata@med.kagawa-u.ac.jp.
authors.forename: Jun
authors.initials: J
authors.lastname: Kunikata
authors.affiliation: Department of Pediatrics, Faculty of Medicine, Kagawa University, Kagawa, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Okada
authors.affiliation: Department of Pediatrics, Faculty of Medicine, Kagawa University, Kagawa, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Itoh
authors.affiliation: Department of Pediatrics, Faculty of Medicine, Kagawa University, Kagawa, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kusaka
mesh_terms: D000293:Adolescent; D000375:Aging / Q000652:urine*; D015415:Biomarkers / Q000652:urine; D002648:Child; D002657:Child Development / Q000502:physiology*; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid; D003306:Coproporphyrins / Q000652:urine*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D000089762:Multidrug Resistance-Associated Protein 2; D012189:Retrospective Studies
chemical_list: C000715087:ABCC2 protein, human; D015415:Biomarkers; D003306:Coproporphyrins; D000089762:Multidrug Resistance-Associated Protein 2; C026971:coproporphyrin III; C031467:coproporphyrin I
keywords: ATP-binding cassette, sub-family C, member 2; bilirubin; children; coproporphyrin; high-performance liquid chromatography