title: Albumin-binding capacity (ABiC) is reduced in patients with chronic kidney disease along with an accumulation of protein-bound uraemic toxins.
abstract: BACKGROUND
  Albumin is an important transport protein for non-water-soluble protein-bound drugs and uraemic toxins. Its transport capacity is reduced in patients with advanced chronic kidney disease (CKD) and unbound fractions of uraemic toxins are related to complications of CKD. We investigated whether this reduction could be quantified and how it correlated with the stages of CKD. Albumin-binding capacity (ABiC) is a dye-based method that quantifies the remaining binding capacity of one major binding site (site II) of the albumin molecule.
  
  
  METHODS
  Blood samples from 104 CKD patients were incubated with a binding site-specific fluorescent marker and the amount of unbound marker was determined by means of fluorescence detection after filtration. Measurements in a pooled human plasma were used for reference. Glomerular filtration rate and serum indoxyl sulphate (IS) levels were also determined.
  
  
  RESULTS
  Impairment of renal function was associated with a reduction in ABiC (mean ± SD: 118 ± 12; 111 ± 11; 99 ± 8 and 79 ± 9% for Stages 1/2, 3, 4 and 5, respectively; P < 0.001) and an increase in IS (3.9 ± 1.1; 6.2 ± 3.2; 16.3 ± 14.9 and 56.1 ± 28.6 μmol/L for Stages 1/2, 3, 4 and 5, respectively; P < 0.001). In dialysis patients, ABiC was lower in those with urine outputs <500 mL/day than in those with preserved urine output (73.7 ± 6.0 versus 83.8 ± 8.5%; P < 0.001).
  
  
  CONCLUSIONS
  Impaired albumin function in CKD patients can be quantified, is related to severity of kidney disease and is associated with an accumulation of uraemic albumin-bound retention solutes.
authors.affiliation: Division of Nephrology, Department of Medicine II, Medical Faculty of the University of Rostock, Rostock, Germany. sebastian.klammt@med.uni-rostock.de
authors.forename: Sebastian
authors.initials: S
authors.lastname: Klammt
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Wojak
authors.forename: Andrea
authors.initials: A
authors.lastname: Mitzner
authors.forename: Sebastian
authors.initials: S
authors.lastname: Koball
authors.forename: Joachim
authors.initials: J
authors.lastname: Rychly
authors.forename: Emil C
authors.initials: EC
authors.lastname: Reisinger
authors.forename: Steffen
authors.initials: S
authors.lastname: Mitzner
mesh_terms: D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D005456:Fluorescent Dyes / Q000378:metabolism*; D005500:Follow-Up Studies; D006801:Humans; D007676:Kidney Failure, Chronic / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012709:Serum Albumin / Q000378:metabolism*; D014118:Toxins, Biological / Q000378:metabolism*; D014511:Uremia / Q000378:metabolism*
chemical_list: D005456:Fluorescent Dyes; D012709:Serum Albumin; D014118:Toxins, Biological