Pre-exposure of mice to low dose or low dose rate ionizing radiation reduces chromosome aberrations induced by subsequent exposure to high dose of radiation or mitomycin C.

The phenomenon of cytogenetic adaptive and cross-adaptive response induced by low dose irradiation and chemical mutagen in mice is described. We found, firstly, that adaptation can be induced by acute low dose X-irradiation (0-100 mGy). Secondly, a cross-adaptation can occur between X-irradiation and mitomycin C (MMC). And finally, mice pre-exposed to chronic low dose rate 60Co-Gamma irradiation (0-226.0 mGy/day) are less susceptible to chromosome aberration induced by subsequent acute higher X-irradiation. Therefore, our data suggest that radioadaptive response depends on dose, dose rate and time interval. Possible mechanisms are also discussed.