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 (S(1); 10 mg/kg/day, S₂; 100mg/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.