Dose-dependent effect of nutritional sulfite intake on visual evoked potentials and lipid peroxidation

The aim of this study was to clarify the dose-dependent effect of sulfite (SO32−) ingestion on brain and retina by means of electrophysiological and biochemical parameters. Fifty two male Wistar rats, aged 3 months, were randomized into four experimental groups of 13 rats as follows; control (C), sulfite treated groups (S1; 10 mg/kg/day, S2; 100 mg/kg/day, S3; 260 mg/kg/day). Control rats were administered distilled water, while the other three groups were given sodium metabisulfite (Na2S2O5) of amounts mentioned above, via gavage for a period of 35 days.All components of visual evoked potential (VEP) were prolonged in S2 and S3 groups compared with S1 and C groups. Plasma-S-sulfonate levels, which are an indicator of sulfur dioxide (SO2) exposure, were increased in Na2S2O5 treated groups in a dose-dependent manner. Furthermore, the significant increments in thiobarbituric acid reactive substances (TBARS) and 4-hydroxy-2-nonenal (4-HNE) levels occurred with increasing intake of Na2S2O5. Though not significant, glutathione (GSH) and oxidized glutathione (GSSG) levels were observed to decrease with increasing doses of Na2S2O5.In conclusion, Na2S2O5 treatment in rats caused a dose-dependent increase in lipid peroxidation and all VEP latencies. The data indicate that lipid peroxidation could play an important role in sulfite toxicity.