Chromosome Abnormalities in Liver and Marrow of Mice Irradiated with Fast Neutrons, Gamma Rays, and X-Rays: Effect of Dose Rate

Abstract

Low-dose-rate irradiation with either [alpha]-rays (1000 rads) or fast neutrons (240 rads or 480 rads) resulted in fewer cells with chromosome abnormalities in mouse liver and bone marrow than did comparable high-dose-rate irradiation with X-rays (500 rads) or neutrons (200 rads or 320 rads). Neutrons generally produced more aberrant cells than did the low-LET radiations, but a dose-rate effect was apparent with both types of radiation. Liver cells with unstable chromosome aberrations, as well as total aberrant liver cells, were less frequent in the low-dose-rate groups. Possible reasons for the observed dose-rate effects are considered, as well as limitations of the experimental system, in which carbon tetrachloride was used to initiate liver cell mitosis. The hipatic results were influenced by the damaging effect of the CCl4 on liver chromosomes and by the presence of dividing myeloid cells in the liver preparations. The marrow data were affected by cell selection phenomena during postirradiation regeneration.