PLASMA-CONCENTRATIONS OF VITAMIN-C, VITAMIN-E AND OR MALONDIALDEHYDE AS MARKERS OF OXYGEN-FREE RADICAL PRODUCTION DURING HEMODIALYSIS/

To investigate the effects of neutrophil activation during hemodialysi s (HD), blood markers of oxygen free radical (OFR) activity were studi ed. Two groups of HD patients on standard cuprophane treatment were in vestigated after an overnight fast. In the first group (mean age 68 +/ - 8 years; n = 6) vitamin supplementation was withdrawn two weeks prio r to the study, whereas the second group (mean age 73 +/- 3 years; n = 7) continued their normal vitamin intake. The two control groups, one consisting of age-matched subjects (mean age 72 +/- 2 years; n = 21), the other of younger subjects (mean age 36 +/- 7 years; n = 11), were asked to cease vitamin supplementation two weeks before the study and to fast overnight before blood sampling. Serial blood and dialysate s amples were collected during HD in the vitamin-deprived patient group, and a single blood sample was collected in the other three groups. Pl asma concentrations of vitamin C (total and reduced form), vitamin E ( alpha-tocopherol) and malondialdehyde (MDA) were determined with newly adopted and validated HPLC methods. Basal plasma vitamin C concentrat ions were lower among vitamin-deprived HD patients than among age-matc hed controls or vitamin-supplemented HD patients (22 +/- 6 mu M versus 39 +/- 19 mu M and 34 +/- 10 mu M, respectively). During a 3-hour HD session, the mean decrease in total vitamin C was 40%. Basal cr-tocoph erol concentrations did not differ significantly between vitamin-depri ved HD patients and vitamin-supplemented HD patients or age-matched co ntrols (39 +/- 5 mu M versus 40 +/- 11 mu M and 38 +/- 6 mu M, respect ively), but were lower in younger controls (33 +/- 4 mu M) No alpha-to copherol was detected in the dialysate, and its plasma concentration d id not change significantly during a single HD session. Basal plasma M DA concentrations were higher in vitamin-supplemented HD patients than in vitamin-deprived HD patients or age-matched controls (1.5 +/- 0.2 mu M versus 0.9 +/- 0.2 mu M and 1.1 +/- 0.2 mu M, respectively). No M DA was detected in the dialysate, and its plasma concentration did not change significantly during a single HD session. Our results indicate an increased need of vitamin C supplementation in HD patients. The co ncentration of oxidized vitamin C seems to peak early during HD and ma y be of value as a marker of OFR production. alpha-tocopherol concentr ations do not change during HD and do not differ from those in control subjects. MDA may increase over a longer period of time on dialysis, but does not change during a single HD treatment.