Gene Expression Changes in the Spleen, Lungs, and Liver of Wistar Rats Exposed to β-Emitted SiO Particles.

To understand the biological effects of residual radioactivity after the atomic bomb explosion in Hiroshima and Nagasaki, we previously investigated the effects of Mn, a major residual radioisotope. Our rat study demonstrated that inhalation exposure to MnO microparticles affected gene expression in the lungs, testes, and liver, despite the low radiation doses. Because Mn is a β- and γ-emitter, the differential effects between β- and γ-rays should be clarified. In this study, Si, a β-emitter with a radioactive half-life similar to that of Mn, was used to determine its effects. Male Wistar rats were exposed to sprayed neutron-activated SiO microparticles, stable SiO microparticles, or X-rays. The animals were examined on days 3 and 14 after irradiation. The expression of radiation-inducible marker genes, including , , and , was measured in the spleen, lungs, and liver. Furthermore, the expressions of pathophysiological marker genes, including , , and in the lungs and , , and in the liver, were determined. Impacts of SiO exposure were observed mainly in the liver, where the expression of markedly increased on post-exposure days 3 and 14. Our data suggest that internal exposure to β-emitted microparticles has significant biological effects and its possible roles as residual radiation after atomic bombing.