Kidney function and plasma copeptin levels in healthy kidney donors and autosomal dominant polycystic kidney disease patients.
BACKGROUND AND OBJECTIVES
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.


DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS
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.
['Zittema|Debbie|D|', 'van den Berg|Else|E|', 'Meijer|Esther|E|', 'Boertien|Wendy E|WE|', 'Muller Kobold|Anneke C|AC|', 'Franssen|Casper F M|CF|', 'de Jong|Paul E|PE|', 'Bakker|Stephan J L|SJ|', 'Navis|Gerjan|G|', 'Gansevoort|Ron T|RT|']
D000328:Adult D005260:Female D006020:Glycopeptides D006801:Humans D007668:Kidney D007677:Kidney Function Tests D008297:Male D008875:Middle Aged D016891:Polycystic Kidney, Autosomal Dominant D012720:Severity of Illness Index D014019:Tissue Donors
vasopressin urea ADPKD cystic kidney