X-Ray-Induced Chromosome Aberrations and Reproductive Death in Mammalian Cells

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Abstract
Data on the rates of spontaneous and induced chromosome aberrations in mammalian cells in vitro and in vivo, as well as the possible role of such chromosome aberrations in radiation-induced mammalian cell death have been examined. The kinetics of X-ray induction of aberrations is similar to that studied extensively in plant material. In particular, the shapes of dose curves for one-and two-hit aberrations are similar in both types of material, as are the distributions per cell of the various types of aberration. It is concluded that there is no threshold dose for aberrations and that the dose required to produce one break per cell in irradiated human epithelioid cells in vitro is about 190 r. This dose is similar to that required to produce one break per cell in mammalian cells in vivo, but much higher than the value for "fibroblast-like cells" in vitro. Studies of the X-ray survival kinetics of a hypotetraploid human cell line similar to that used in previous studies have shown that the survival of these cells better fits a compound expression containing both one- and two-hit components than a simple sigmoidal curve. The hypothesis that two-break chromosome aberration production is the entire, or a major, cause of mammalian cell death is examined in the light of the quantitative data available, and is rejected.