主催: The Japan Radiation Research Society
Low LET radiation generates toxic free radicals and the radical-induced injury to nulear DNA makes serious damages in living cells. Although endogenous mechanisms to diminish toxicity of the free radicals are studied in the cell-free system, their function in the living cells are not clarified. To reveal the initial damages and the protection mechanism, we established the method to quantitate radiation damage and the radioprotection in the living cells. When murnie macrophage-like cell line RAW264.7 was used, x-ray-induced nuclear damage could be measured reporducibly with limited deviation. The frequencies of both micronucleated and growth-inhibited cells were increased by x-ray of doses from 0.2 to 3.0 Gy at dose-dependent manner. Among various antioxidative compunds, thiols showed the most protective effect on both the micronucleation and growth-inhibition. It was suggested the protection levels were dependent upon not only the membrane permeability of the molecule but also the effect to modify the intracellular thiol levels. When constitutive exprssion gene for glutathion peroxidase with modification in amino acid sequence were stably introduced into the cells, radiation-induced growth inhibition was decreased. These results show contribution of the regulation of intracellular thiols to the nuclear damage by ionizing radiation.
