Journal Article

Convective and diffusive losses of vitamin C during haemodiafiltration session: a contributive factor to oxidative stress in haemodialysis patients

Marion Morena, Jean‐Paul Cristol, Jean‐Yves Bosc, Ciro Tetta, Gilles Forret, Claude‐Louis Leger, Cécile Delcourt, Laure Papoz, Bernard Descomps and Bernard Canaud

in Nephrology Dialysis Transplantation

Published on behalf of European Renal Association - European Dialysis and Transplant Assoc

Volume 17, issue 3, pages 422-427
Published in print March 2002 | ISSN: 0931-0509
Published online March 2002 | e-ISSN: 1460-2385 | DOI: http://dx.doi.org/10.1093/ndt/17.3.422
Convective and diffusive losses of vitamin C during haemodiafiltration session: a contributive factor to oxidative stress in haemodialysis patients

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Background. Enhanced oxidative stress in haemodialysis (HD) patients may be considered as a risk factor for accelerated atherosclerosis. Reduced antioxidant defences include impairment in enzyme activities and decreased plasma levels of hydrophilic vitamin C (vit C), and cellular levels of lipophilic vitamin E (vit E).

Methods. We investigated plasma levels of vit C in 19 patients undergoing regular haemodiafiltration (HDF) (mean age 62±7 years) and in 1846 healthy elderly subjects (HS) (mean age 69±5 years). The contribution of convection and diffusion was determined using paired filtration dialysis (PFD), a modified HDF technique which physically separates convective from diffusive fluxes. Blood samples were collected before and after the HDF session; in addition at 60 min of HDF, samples were drawn from arterial lines (AL) and venous lines (VL), dialysate (D) and ultrafiltrate (UF). Blood levels of total vit C were determined using an HPLC fluorescence method. Markers of oxidative stress were also assessed in both populations as follows: levels of malondialdehyde (MDA) were determined by fluorometric assay, measurements of advanced oxidation protein products (AOPP) and glutathione peroxidase (GSH‐Px) activity were performed by spectrophotometric assay, and plasma vit E content was obtained by an HPLC procedure.

Results. A significant reduction in plasma vit C level was observed in HDF patients when compared with HS (1.6±1.4 μg/ml in HDF vs 6.6±3.7 μg/ml in HS; P<0.01). The HDF session was associated with a dramatic reduction in vit C levels (1.87±1.57 μg/ml before HDF and 0.98±0.68 μg/ml after HDF); at 60 min of HDF, concentrations were as follows: AL=1.35±1.27 μg/ml; VL=0.37±0.31 μg/ml, D=0.40±0.34 μg/ml, UF=1.24±1.18 μg/ml; corresponding to a diffusive flux of 271 μg/min and a convective flux of 126 μg/min. Total loss of vit C could be assessed at 66 mg/session (8–230 mg/session). According to this loss of vit C, presence of an oxidative stress was demonstrated in HD population as shown by a significant increase in MDA (1.66±0.27 μM in HD vs 0.89±0.25 μM in HS; P<0.01) and AOPP (77.5±29.3 μM in HD vs 23.5±13.2 μM in HS; P<0.01) levels, and a decrease in GSH‐Px activity (259.2±106.3 U/l in HD vs 661.2±92.2 U/l in HS; P<0.01). No change in plasma vit E between both populations (30.7±9.1 μM in HD vs 35.3±7.34 μM in HS) was observed.

Conclusions. These results suggest that HDF with highly permeable membranes is associated with a significant loss of vit C. Diffusive transport is responsible for two‐thirds whereas convective phenomenon accounts for only one‐third of this loss.

Keywords: antioxidant; haemodiafiltration; oxidative stress; vitamin C

Journal Article.  3698 words.  Illustrated.

Subjects: Nephrology

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