title: Urine Concentrating Capacity, Vasopressin and Copeptin in ADPKD and IgA Nephropathy Patients with Renal Impairment.
abstract: BACKGROUND
  Autosomal Dominant Polycystic Kidney Disease (ADPKD) patients have an impaired urine concentrating capacity. Increased circulating vasopressin (AVP) concentrations are supposed to play a role in the progression of ADPKD. We hypothesized that ADPKD patients have a more severely impaired urine concentrating capacity in comparison to other patients with chronic kidney disease at a similar level of kidney function, with consequently an enhanced AVP response to water deprivation with higher circulating AVP concentrations.
  
  
  METHODS
  15 ADPKD (eGFR<60) patients and 15 age-, sex- and eGFR-matched controls with IgA nephropathy (IgAN), underwent a water deprivation test to determine maximal urine concentrating capacity. Plasma and urine osmolality, urine aquaporin-2 (AQP2) and plasma AVP and copeptin (a surrogate marker for AVP) were measured at baseline and after water deprivation (average 16 hours). In ADPKD patients, height adjusted total kidney volume (hTKV) was measured by MRI.
  
  
  RESULTS
  Maximal achieved urine concentration was lower in ADPKD compared to IgAN controls (533±138 vs. 642±148 mOsm/kg, p = 0.046), with particularly a lower maximal achieved urine urea concentration (223±74 vs. 299±72 mmol/L, p = 0.008). After water deprivation, plasma osmolality was similar in both groups although change in plasma osmolality was more profound in ADPKD due to a lower baseline plasma osmolality in comparison to IgAN controls. Copeptin and AVP increased significantly in a similar way in both groups. AVP, copeptin and urine AQP2 were inversely associated with maximal urine concentrating in both groups.
  
  
  CONCLUSIONS
  ADPKD patients have a more severely impaired maximal urine concentrating capacity with a lower maximal achieved urine urea concentration in comparison to IgAN controls with similar endogenous copeptin and AVP responses.
authors.affiliation: Department of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Debbie
authors.initials: D
authors.lastname: Zittema
authors.affiliation: Department of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Niek F
authors.initials: NF
authors.lastname: Casteleijn
authors.affiliation: Department of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Stephan J L
authors.initials: SJ
authors.lastname: Bakker
authors.affiliation: Department of Clinical Chemistry, IJsselland Ziekenhuis, Capelle aan den IJssel, The Netherlands.
authors.forename: Lianne S M
authors.initials: LS
authors.lastname: Boesten
authors.affiliation: Department of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: A A Margreeth
authors.initials: AA
authors.lastname: Duit
authors.affiliation: Department of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Casper F M
authors.initials: CF
authors.lastname: Franssen
authors.affiliation: Department of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Carlo A J M
authors.initials: CA
authors.lastname: Gaillard
authors.affiliation: Department of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Ron T
authors.initials: RT
authors.lastname: Gansevoort
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D051399:Aquaporin 2 / Q000652:urine; D005260:Female; D005922:Glomerulonephritis, IGA / Q000000981:diagnostic imaging / Q000652:urine*; D006020:Glycopeptides / Q000652:urine*; D006801:Humans; D007671:Kidney Concentrating Ability; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D016891:Polycystic Kidney, Autosomal Dominant / Q000000981:diagnostic imaging / Q000652:urine*; D014667:Vasopressins / Q000652:urine*
chemical_list: C496023:AQP2 protein, human; D051399:Aquaporin 2; D006020:Glycopeptides; C048197:copeptins; D014667:Vasopressins