title: The postdialytic rise in the plasma total homocysteine concentration is delayed.
abstract: OBJECTIVE
  The mechanism behind the uremic hyperhomocysteinemia has not been elucidated. Possibly, dialyzable uremic toxins play a role, e.g. as enzyme inhibitors. If so, the conditions for enzymatic removal would be expected to improve after dialysis. Therefore, we studied the postdialytic pattern of the plasma total homocysteine (tHcy) concentration.
  
  
  METHODS
  We collected blood samples from 19 stable, vitamin-supplemented hemodialysis patients before and at 5, 60, as well as at 480 min after a dialysis session. The patients were studied after dialysis with a low-flux dialyzer (Polyflux 6L) and a high-flux dialyzer (Polyflux 14S).
  
  
  RESULTS
  The mean predialytic plasma tHcy concentration was 13.3 micromol/l which is considerably lower than the concentrations observed in our previous studies. In all patients, the plasma tHcy concentration fell during treatment with both types of dialyzers (average decrease 28 +/- 7%, p < 0.0001, and 31 +/- 8%, p < 0.0001, respectively). No postdialytic change in the plasma tHcy concentration was observed at 60 min after low-flux dialysis, however, after high-flux dialysis, the plasma tHcy concentration was significantly lower at 60 min postdialysis than at 5 min (3 +/- 8%, p < 0.05). At 480 min after dialysis, a significant postdialytic increase in the plasma tHcy concentration was found (6 +/- 9%, p < 0.01, and 11 +/- 5%, p < 0.0001, respectively) both in the case of low-flux and high-flux treatment.
  
  
  CONCLUSIONS
  In the postdialytic phase, we observed a short-lived stability in the plasma tHcy concentration, and in the case of high-flux dialysis, even a slight decrease in the plasma tHcy concentration. The results support the hypothesis that dialyzable substances interfere with homocysteine removal.
authors.affiliation: Department of Medicine, Landspitali University Hospital Hringbraut, Reykjavik, Iceland. margreta@rsp.is
authors.forename: Margret
authors.initials: M
authors.lastname: Arnadottir
authors.forename: Kerstin
authors.initials: K
authors.lastname: Wingren
authors.forename: Björn
authors.initials: B
authors.lastname: Hultberg
authors.forename: Jörgen
authors.initials: J
authors.lastname: Hegbrant
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000553:Ambulatory Care; D003404:Creatinine / Q000097:blood; D005260:Female; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D006435:Renal Dialysis / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D012212:Rheology; D013997:Time Factors; D014815:Vitamins / Q000008:administration & dosage / Q000097:blood
chemical_list: D014815:Vitamins; D006710:Homocysteine; D003404:Creatinine