Retinol and alpha-tocopherol in hemodialysis patients

The biological effects of reactive oxygen species and other radicals controlled by antioxidant mechanisms are modified by various enzymes and other substrates. Antioxidant substrates are divided into those with lipophilic and hydrophilic groups. Retinol and tocopherol are the main representations of lipophilic antioxidants. The aim of the present study was to describe the changes of retinol and alpha-tocopherol which occurred in hemodialysis (HD) patients in respect to the influence of antioxidant systems. The experimental group consisted of 14 patients on regular HD treatment. The control group consisted of 14 healthy blood donors. HPLC was used to measure retinol and alpha-tocopherol in serum. We found that the retinol concentration was significantly higher in HD patients compared to controls (2.35 +/- 0.95 versus 0.90 +/- 0.23 mg/L, p < 0.0001). The concentration of alpha-tocopherol in serum was not different in both study groups (7.32 +/- 3.01 versus. 8.94 +/- 3.57 mg/L). A review of the MEDLINE database since 1985 found a few references concerning these important antioxidant vitamins in HD patients and these contained contrasting results. It has been suggested that some of the complications related to HD including cardiovascular complications, anemia and atherosclerosis may be due to ineffective antioxidant systems and/or to increased free oxygen radical production. The question about supplementation of antioxidants in HD patients is open although there are some positive data regarding the use of moderate and safe selenium supplementation in HD patients. HD patients treated by erythropoietin had increased plasma concentration of retinol and normal level of alpha-tocopherol compared to healthy group. However, this positive finding did not affect lipid peroxidation, which is increased in HD patients and leads to some complications during HD treatment.