Absence of genomic instability in mice following prenatal low dose-rate gamma-irradiation.

Purpose: To determine whether mice exposed to an extended low dose of gamma-irradiation during most of their prenatal period express increased frequencies of micronucleated polychromatic erythrocytes (fMPCE) and/or micronucleated normochromatic erythrocytes (fMNCE) several weeks after the end of irradiation.

Methods: Female CBA/Ca mice were gamma-irradiated for an average of 16 days during their pregnancy. The mice were exposed to dose rates of 0, 44, 99 and 265 mGy/day. At 1-2 days prior to parturition the mice were removed from exposure. Then, 36 days after birth, peripheral blood was drawn from all offspring (74 mice). Using flow-cytometer-based analysis, the frequencies of MPCE and MNCE were determined. From each animal about 170,000 PCE were analysed.

Results: No delayed effects in terms of higher fMPCE or fMNCE were observed among the in utero exposed mice of either gender. On the contrary, a significant (p<0.001) reduction of fMPCE was found among the male offspring exposed at the highest dose rate.

Conclusion: Gamma-irradiation of mice during their prenatal stage did not induce damage in erythroid stem cells that can be detected as persistent or delayed chromosome aberrations (i.e. micronucleated erythrocytes) at 35 days after the end of exposure.