Lifetime persistence and clonality of chromosome aberrations in the peripheral blood of mice acutely exposed to ionizing radiation

As the measurement of chromosomal translocations increases in popularity fo r quantifying prior radiation exposure, information on the possible decline of these "stable" aberrations over time is urgently needed. We report here information about the persistence of radiation-induced chromosome aberrati ons in vivo over the life span of a rodent. Female C57BL/6 mice were given a single whole-body acute exposure of 0, 1, 2, 3 or 4 Gy Cs-137 gamma rays at 8 weeks of age. Chromosome aberrations were analyzed from peripheral blo od samples at various intervals between 1 day and 21 months after exposure. Aberrations were detected by painting chromosomes 2 and 8, Translocations decreased dramatically during the first 3 months after irradiation, beyond which time the frequencies remained relatively constant out to 1 year, when the effects of aging and clonal expansion became significant. Both recipro cal and nonreciprocal translocations increased with age in the unexposed co ntrol animals and were involved in clones. As expected of unstable aberrati ons, dicentrics decreased rapidly after exposure and reached baseline level s within 3 months. These results indicate that the persistence of transloca tions induced by ionizing radiation is complicated by aging and clonal expa nsion and that these factors must be considered when quantifying translocat ions at long times after exposure. These results have implications for biol ogical dosimetry in human populations. (C) 2000 by Radiation Research Socie ty.