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

Abstract

The kinetics of x-ray-induced chromosome aberrations in mammalian cells were found to be similar to that in plants. In particuiar, the shapes of dose curves for oneand two-break aberrations are similar in both types of material, as are the distributions per cell of the various types of aberration. It may be concluded that there is no threshold dose for aberrations and random samples of damage are obtained from cells sampled at the first postirradiation metaphase. The dose required to produce one break per cell in irradiated human diploid epithelioid cells in vitro was calonlated to be about 190 r. This dose is similar to the dose required to produce one break per cell in mammalian cells in vivo, but much higher than the value for flbroblasts in vitro. Studies of the x-ray survival genetics of a hypotetraploid human cell line similar to that used in other studies have shown that the survival of these cells better fits a compound curve containing both single- and multiple-hit oomponents than a simple sigmoidal curve. Data on the numbers of cells not having x-ray-induced 2hit chromosome aberrations show that these cells do not fit the quantitative pattern required by the hypothesis that x-ray-induced cellmore » killing is caused mainly by the production of visible 2-hdt chromosome aberrations. Although it is reasonable to assume that these aberrations cause a proportion of such killing, their relation to killing is obsource, and certainly other targets, beth oytoplasrnic and nuclear, should be taken into consideration. 31 references, (auth)« less