GENOMIC INSTABILITY IN CHINESE-HAMSTER CELLS AFTER EXPOSURE TO X-RAYSOR ALPHA-PARTICLES OF DIFFERENT MEAN LINEAR-ENERGY-TRANSFER

Evidence has accumulated that radiation induces a transmissible persis tent destabilization of the genome, which mag. result in effects arisi ng in the progeny of irradiated but surviving cells. An enhanced death rate among the progeny of cells surviving irradiation persists for ma ny generations in the form of a reduced plating efficiency. Such delay ed reproductive death is correlated with an increased occurrence of mi cronuclei. Since it has been suggested that radiation-induced chromoso mal instability might depend on the radiation quality, we investigated the effects of alpha particles of different LET by looking at the fre quency of delayed micronuclei in Chinese hamster V79 cells after cytoc halasin-induced block of cell division, A dose-dependent increase in t he frequency of micronuclei was found in cells assayed 1 week postirra diation or later. Also, there was a persistent increase in the frequen cy of dicentrics in surviving irradiated cells, Moreover, we found an increased micronucleus frequency in all of the 30 clones isolated from individual cells which had been irradiated with doses equivalent to e ither one, two or three alpha-particle traversals per cell nucleus, We conclude that the target for genomic instability in Chinese hamster c ells must be larger than the cell nucleus. (C) 1997 by Radiation Resea rch Society