Alteration in plasma antioxidant capacities in chronic renal failure and hemodialysis patients: a possible explanation for the increased cardiovascular risk in these patients

Objective: The high incidence of cardiovascular diseases in chronic renal f ailure (CRF) and hemodialyzed (HD) patients is now well established and the involvement of oxidative stress has been hypothesized in these phenomena. The aim of our study was to evaluate the level of oxidative stress in healt hy controls (CTL) compared with CRF and HD patients before (pre-HD) and aft er (post-HD) the dialysis session, carried out on a high biocompatible poly acrylonitrile membrane AN69. Methods: Several indicators of the extracellul ar redox status were evaluated in plasma. The ascorbyl free radical (AFR) w as directly measured using electron spin resonance spectroscopy (ESR) and e xpressed with respect to the vitamin C level to obtain a direct index of ox idative stress. Indirect plasma parameters such as vitamin E, thiol and uri c acid levels were also quantified. The plasma antioxidant status (PAS) was evaluated by the allophycocyanin test. Nitric oxide (NO) stable-end metabo lites: nitrites and nitrates (NOx), were measured in plasma. Results: In CR F patients, vitamin C and thiol levels were low, and the AFR/vitamin C rati o high compared with the CTL. On the other hand, PAS and uric acid levels w ere shown to be higher in CRF patients. After the dialysis session, vitamin C level decreased and AFR/vitamin C ratio increased. The thiol levels were shown to be increased, in return PAS and uric acid levels were significant ly lower after the dialysis session. NOx levels rose during CRF, but were s ignificantly decreased after the dialysis procedure. No differences in vita min E status were observed between CTL, CRF and HD patients. Conclusion: Ou r study demonstrates that profound disturbances in the extracellular redox system occur during the course of chronic renal failure and hemodialysis, a nd may provide an explanation for the cardiovascular complications in these patients. (C) 2000 Elsevier Science B.V. All rights reserved.