Genetic effects in somatic cells of mice exposed to chronic low dose γ-irradiation, and their progeny

In order to reveal specific features of biological impact of low dose ionizing radiation, we studied genetic effects in bone marrow and thyroid gland cells in animals after exposure to low dose radiation, and also traced the possibility of the inheritance of radiation-induced changes in the progeny of animals of the first generation (F1). To assess genetic disorders in both organs, we used micronuclear test and DNA-comet approach (neutral version), we also determined mitotic index and the proportion of cells eliminated by apoptosis in the bone marrow. The study was performed using 160 adult mice of the Af line from the experimental animal nursery of the Institute of Biology, Komi Science Centre, Ural Branch, RAS. The animals were exposed to γ-irradiation during 29, 53 and 84 days using the dose of 150 μGy/h. The total absorbed dose was 10, 20 and 30 Gy consequently. The material for analyses was taken from F1 progeny, obtained from irradiated and control animals of 2-3 month age. As a result of molecular and cytogenetic analyses, the features of the effect of chronic γ-irradiation at used doses on the damage level of the genome of cells with different proliferative activity were revealed. Four months after the exposure to ionizing radiation changes were found in proportion of double-strand DNA breaks in somatic cells of animals at frequency of occurrence of cells with micronuclei in both organs being within normal. More pronounced cytogenetic effects were found in bone marrow in comparison with the thyroid gland, where there is marked nonlinear dependence of manifestation of genomic instability from the exposure dose. The results obtained from the progeny (F1) confirm the data on the heritability of the effects of radiation-induced gеnomic instability.