Effects of Ingested Sulfite on Glutamate Synthesis and Release in the Rat Hippocampus

While the negative effects of sulfite on learning and memory are shown in experimental studies; the mechanisms of effects are unknown. We investigated the role of glutamate, glutamine, glutaminase and glutamine synthetase levels, vesicular glutamate transporter (VGLUT1) and excitatory amino acid transporters (EAAT1, EAAT2) in these effects of sulfite. Forty male Wistar albino rats were randomly assigned into two groups: control (C) and sulfite (S). S group animals were fed with freshly prepared sulfite via gastric gavage (25 mg/kg/day) for 35 days while the C group received equal volumes of distilled water via the same way and period. Microdialysis probe was placed in rat hippocampus for extracellular fluid sampling. The extracellular glutamate and glutamine concentrations were measured by Mass spectrometry. The glutaminase and glutamine synthetase levels as well as VGLUT1 and EAATs were analyzed on the hippocampi. In the hippocampus, the levels of glutaminase and glutamine synthetase of the S group decreased with respect to C group but the levels of extracellular glutamate and glutamine together with expression of VGLUT1, EAAT1 and EAAT2 mRNA did not change. It has been observed that 25 mg/kg dose of sulfite reduces glutamine synthetase and glutaminase, which are very important for the maintenance of the glutamine/glutamate cycle. In order to reveal the glutamate-mediated effects of sulfite in the hippocampus, it is necessary to examine the dose-dependent effects of sulfite and analyze the glutamate and glutamine levels in homogenates of hippocampus tissue.