Persistence of Chromatid Aberrations in the Cells of Solid Mouse Tissues Exposed to 137Cs Gamma Radiation

Primary mouse ear and kidney cultures were established for determination of cytogenetic aberrations at short (3 days to 1 month) and long (12-23 months) times after exposure of their right sides to 7.5 Gy of 137Cs gamma radiation. In every case, higher levels of aberrations were observed in primary cultures established from the irradiated tissues than in those established from the contralateral tissues. The most common aberrations in the contralateral tissues and those from nonirradiated mice were chromatid and isochromatid breaks and small chromatid fragments. Primary cells from irradiated tissues removed from animals within a month of exposure displayed a variety of unstable chromosome-type aberrations characteristic of recent exposure to ionizing radiation including rings, dicentrics, double minutes, and large acentric fragments. The percentages of cells exhibiting chromatid breaks and small chromatid fragments were also markedly elevated. Although the levels of chromosome-type aberrations found in primary cells from irradiated tissues dropped to near background levels a year or more after exposure, chromatid-type aberrations remained elevated. These results are consistent with long-term persistence of damage in the genomes of ionizing radiation-exposed cells in solid tissues and the induction of genomic instability in vivo.