Selenium and glutathione peroxidase mRNA in rat glioma.

The purpose of current study was to determine the step at which dietary selenium (Se) regulates the transcriptional expression of the gene for Se-glutathione peroxidase (Se-GPx) in rat brain and transplanted glioma tissue. Wistar rats were fed a Se-free diet or the same diet supplemented with 0.5, 2.0, and 4.0 mg Se/kg as sodium selenite for at least 3 wk. Then, the rats were transplanted with C6 rat glioma cells into the right frontal lobe parenchyma. All rats were observed for 30 d, then tumor and contralateral brain tissue were excised and divided into three portions for purification of selenium content, for the assay of Se concentration, Se-GPx activity, and for Se-GPx mRNA. Se concentration and Se-GPx activity are increased with Se supplementation both in tumor tissue and contralateral brain tissue, and Se concentration in tumor is higher than that in contralateral brain tissue at each dietary Se content. Se-GPx mRNA of brain and tumor were probed with fragments from a rat Se-GPx cDNA in Northern blot analysis. There was significant differences of Se-GPx mRNA transcription in brain tumor tissue among each dietary group of the Se content, and the steady-state level of Se-GPx mRNA was markedly reduced by Se deficiency. These results suggest that dietary Se exerts its augmenting effect on Se-GPx gene transcription.