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.