title: Determination of high and low molecular weight molecules of icodextrin in plasma and dialysate, using gel filtration chromatography, in peritoneal dialysis patients.
abstract: OBJECTIVE
  The aim of this study was to apply high performance liquid chromatography (HPLC) with modern gel filtration media to determine high molecular weight (HMW) icodextrin fractions and low molecular weight (LMW) icodextrin metabolites in dialysate and plasma in peritoneal dialysis (PD) patients on treatment with icodextrin, and to explore the potential relationships between these compounds, alpha-amylase activity, and glomerular filtration rate.
  
  
  METHODS
  Retrospective study of dialysate and plasma samples from PD patients.
  
  
  METHODS
  Samples were collected at one PD center.
  
  
  METHODS
  Blood and dialysate samples were obtained from PD patients who were subdivided into three groups: patients using only glucose-based peritoneal dialysis fluid (GPDF; GLU group, n = 23), patients studied after the first long dwell with icodextrin-based peritoneal dialysis fluid (IPDF; 1st ICO group, n = 24), and patients who were regular users of IPDF for the long dwells (ICO group, n = 9).
  
  
  METHODS
  LMW icodextrin metabolites [i.e., maltose (G2), maltotriose (G3), maltotetraose (G4), maltopentaose (G5), maltohexaose (G6), and maltoheptaose (G7)] and HMW fractions were determined in plasma and dialysate using two different gel filtration HPLC methods. Enzymatic hydrolysis with amyloglucosidase to glucose yielded the total carbohydrate content and this was used to validate the HPLC results. alpha-Amylase activity was determined using a routine method.
  
  
  RESULTS
  The results obtained by gel filtration HPLC yielded values of LMW metabolites and HMW fractions in plasma and dialysate in agreement with results obtained with enzymatic hydrolysis. HMW fractions were not detectable in plasma. Absorption of icodextrin from the peritoneal cavity during the long dwell (10 - 16 hours) was, on average, 39% of the amount instilled. During the long dwell, there was a relative decrease in the dialysate concentration of the largest HMW fractions (>21.4 kDa). Plasma concentration of the LMW icodextrin metabolites G2-G7 was highest in the ICO group (2.65+/-0.54 mg/mL) but also higher in the 1st ICO group (1.97+/-0.57 mg/mL) compared with the GLU group (0.52+/-0.23 mg/mL). Plasma alpha-amylase activity was significantly lower in the 1st ICO group and in the ICO group compared with the GLU group.
  
  
  CONCLUSIONS
  Accurate analysis of HMW icodextrin fractions in dialysate and LMW icodextrin metabolites in plasma and dialysate in PD patients can be achieved by gel filtration HPLC with two different columns. This method can be used to study the complex pattern of changes in icodextrin and its metabolites in plasma and dialysate. The finding that HMW icodextrin fractions were not detected in plasma was unexpected, and differs from results of previous studies by other researchers.
authors.affiliation: Department of Clinical Science, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden.
authors.forename: Elvia
authors.initials: E
authors.lastname: García-López
authors.forename: Björn
authors.initials: B
authors.lastname: Anderstam
authors.forename: Olof
authors.initials: O
authors.lastname: Heimbürger
authors.forename: Gianpaolo
authors.initials: G
authors.lastname: Amici
authors.forename: Andrzej
authors.initials: A
authors.lastname: Werynski
authors.forename: Bengt
authors.initials: B
authors.lastname: Lindholm
mesh_terms: D002851:Chromatography, High Pressure Liquid; D005260:Female; D005936:Glucans / Q000032:analysis* / Q000493:pharmacokinetics*; D005947:Glucose / Q000032:analysis* / Q000493:pharmacokinetics*; D015312:Hemodialysis Solutions / Q000032:analysis* / Q000493:pharmacokinetics*; D006801:Humans; D000077607:Icodextrin; D008297:Male; D008875:Middle Aged; D010530:Peritoneal Dialysis; D012189:Retrospective Studies
chemical_list: D005936:Glucans; D015312:Hemodialysis Solutions; D000077607:Icodextrin; D005947:Glucose