title: Kidney function and plasma copeptin levels in healthy kidney donors and autosomal dominant polycystic kidney disease patients.
abstract: OBJECTIVE
  Plasma copeptin, a marker of arginine vasopressin, is elevated in patients with autosomal dominant polycystic kidney disease and predicts disease progression. It is unknown whether elevated copeptin levels result from decreased kidney clearance or as compensation for impaired concentrating capacity. Data from patients with autosomal dominant polycystic kidney disease and healthy kidney donors before and after donation were used, because after donation, overall GFR decreases with a functionally normal kidney.
  
  
  METHODS
  Data were obtained between October of 2008 and January of 2012 from healthy kidney donors who visited the institution for routine measurements predonation and postdonation and patients with autosomal dominant polycystic kidney disease who visited the institution for kidney function measurement. Plasma copeptin levels were measured using a sandwich immunoassay, GFR was measured as (125)I-iothalamate clearance, and urine concentrating capacity was measured as urine-to-plasma ratio of urea. In patients with autosomal dominant polycystic kidney disease, total kidney volume was measured with magnetic resonance imaging.
  
  
  RESULTS
  Patients with autosomal dominant polycystic kidney disease (n=122, age=40 years, men=56%) had significantly higher copeptin levels (median=6.8 pmol/L; interquartile range=3.4-15.7 pmol/L) compared with donors (n=134, age=52 years, men=49%) both predonation and postdonation (median=3.8 pmol/L; interquartile range=2.8-6.3 pmol/L; P<0.001; median=4.4 pmol/L; interquartile range=3.6-6.1 pmol/L; P<0.001). In donors, copeptin levels did not change after donation, despite a significant fall in GFR (from 105 ± 17 to 66 ± 10; P<0.001). Copeptin and GFR were significantly associated in patients with autosomal dominant polycystic kidney disease (β=-0.45, P<0.001) but not in donors. In patients with autosomal dominant polycystic kidney disease, GFR and total kidney volume were both associated significantly with urine-to-plasma ratio of urea (β=0.84, P<0.001; β=-0.51, P<0.001, respectively).
  
  
  CONCLUSIONS
  On the basis of the finding in donors that kidney clearance is not a main determinant of plasma copeptin levels, it was hypothesized that, in patients with autosomal dominant polycystic kidney disease, kidney damage and associated impaired urine concentration capacity determine copeptin levels.
authors.affiliation: Departments of Nephrology and.
authors.forename: Debbie
authors.initials: D
authors.lastname: Zittema
authors.affiliation: Departments of Nephrology and.
authors.forename: Else
authors.initials: E
authors.lastname: van den Berg
authors.affiliation: Departments of Nephrology and.
authors.forename: Esther
authors.initials: E
authors.lastname: Meijer
authors.affiliation: Departments of Nephrology and.
authors.forename: Wendy E
authors.initials: WE
authors.lastname: Boertien
authors.affiliation: Laboratory Medicine, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Anneke C
authors.initials: AC
authors.lastname: Muller Kobold
authors.affiliation: Departments of Nephrology and.
authors.forename: Casper F M
authors.initials: CF
authors.lastname: Franssen
authors.affiliation: Departments of Nephrology and.
authors.forename: Paul E
authors.initials: PE
authors.lastname: de Jong
authors.affiliation: Departments of Nephrology and.
authors.forename: Stephan J L
authors.initials: SJ
authors.lastname: Bakker
authors.affiliation: Departments of Nephrology and.
authors.forename: Gerjan
authors.initials: G
authors.lastname: Navis
authors.affiliation: Departments of Nephrology and r.t.gansevoort@umcg.nl.
authors.forename: Ron T
authors.initials: RT
authors.lastname: Gansevoort
mesh_terms: D000328:Adult; D005260:Female; D006020:Glycopeptides / Q000097:blood*; D006801:Humans; D007668:Kidney / Q000502:physiology*; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D016891:Polycystic Kidney, Autosomal Dominant / Q000097:blood* / Q000503:physiopathology*; D012720:Severity of Illness Index; D014019:Tissue Donors
chemical_list: D006020:Glycopeptides; C048197:copeptins
keywords: ADPKD; cystic kidney; urea; vasopressin