Sulfites, which are commonly used as preservatives, are continuously formed in the body during metabolism of sulfur-containing amino acids. Sulfite is oxidized to sulfate ion by sulfite oxidase (SOX). The aim of this study was to investigate the possible toxic effects of sulfite on neurons by measuring active avoidance learning in normal and SOX-deficient rats.
Forty male wistar rats at aged 24 monthswere used this study Rats were divided four group Control group (C), sulfite group (S), deficient group (D) and deficient + sulfitegroup (DS). Sulfite oxidase deficiency was established by feeding rats a low molybdenum diet and adding 200 ppm tungsten (W) to their drinking water. Sulfite in the form of sodium metabisulfite (Na2O5S2, 25 mg/kg) was given by gastric gavage. Whole treatment schedule were continued for 6 weeks. Active avoidance behavior was studied in the middle of the 6th week. The animals were trained by using an automated shuttle box (Ugo Basile 7502). At the end of experimental period the rats were sacrificed by exsanguination under anesthesia, and their hippocampus and livers quickly removed.

Hepatic SOX activity in deficient groups was measured to confirm SOX deficiency. The hippocampus were used for determining activity of COX enzymes and levels of TBARS and PGE2 and nitrit /nitrat level . SOX deficient rats had an approximately 10-fold decrease in hepatic SOX activity compared with normal rats
Sulfite-have not induced impairment of active avoidance learning in SOX-deficient rats and in normal rats compared with control and deficient group. Sulfite had no effect on TBARS of hippocampus and nitrit /nitrate levels in SOX-deficient and normal groups. Treatment with sulfite is not significantly increased the activity of COX , caspase-3 and PGE2 level in hippocampus when compared to the control group and deficient group