Chromosome damage induced by decay of 3H and 125I incorporated into DNA of Chinese hamster cells.

The present study was undertaken to compare the frequency of chromatid-type aberrations in Chinese hamster cells with previous results on accumulation of unrepaired DNA-strand breaks after incorporation of 3H-TdR or 125IUdR into DNA. A linear-quadratic function was fitted by the weighted-least-square method to the data on yield of chromatid aberrations at different dpm values. Based on a significant linear response at low doses, RBE for 125I in relation to 3H was calculated for (i) chromatid breaks (17 +/- 6), (ii) the sum of isochromatid breaks and chromatid exchanges (21 +/- 9), and (iii) the total number of chromatid aberrations (18 +/- 5). Analogously, the RBE for accumulation of DNA-strand breaks was determined (13 +/- 6). Our results are consistent with the assumption that chromosomal aberrations mainly originate from unrepaired DNA-strand breaks.