Analysis of chromosomal damage after in vivo exposure to 56Fe ions by means of mFISH and micronucleus methods

By means of the blood MN assay, we detected dose-dependent increases in the frequencies of MN in normochromatic erythrocytes (NCE or mature red blood cells) at day 7 following in vivo exposure to 56Fe ions or 137Cs γ rays. In contrast, only a slight increase in the frequency of MN in polychromatic erythrocytes (PCE or immature red blood cells) was detected at day 7 in blood samples of mice exposed to 56Fe ions, but not 137Cs γ rays. The MN-NCE data showed that 56Fe ions were approximately four times more efficient in inducing chromosomal damage than 137Cs γ rays. The results demonstrated the sensitivity of the mouse in vivo MN assay in detecting chromosomal damage that was induced in the bone marrow of mice exposed in vivo to varying doses of 56Fe ions, when appropriate cell types were used for the analysis at a specific time post-irradiation. However, the MN assay is incapable of detecting stable-type chromosomal damage (e.g., translocation) making the MN assay less informative than the mFISH method.