Keywords: chronic exposure, radiation serial effect, low dose radiation, X–rays, DNA damage, structural chromosome aberration test, mammalian cells, repair–deficient mutant cells, low radiation, radiation exposure, DNA double–strand breaks, DSBs, clastogenic effect, ionising radiation, X–ray exposure
Chronic exposure to low–dose of X–rays induces DNA double–strand breaks in mammalian cells
The purpose of present study is to evaluate the induction of clastogenic effect after chronic exposure to low dose of ionising radiation in both CHO–K1 cells and in their DNA Double–Strand Breaks (DSBs)–repair deficient mutant xrs–5. Cells were cultured for 14 dilution cycles and grown to confluency. Radiation treatment was performed once per cycle with 10 mGy X–rays to carry out the structural chromosome aberration test. The results showed a significant increase in the frequency of achromatic lesions (p < 0.001) in CHO–K1 cells. In addition, xrs–5 cells showed an increase of chromatid and chromosome–type aberrations (p < 0.001). Sequential exposure produced a level of DNA damage that is amplified through successive cycles triggering the efficient repair of DSBs. The increased damage in xrs–5 cells provides evidence that the non–homologous end–joining repair of DNA DSBs is involved after low dose X–ray exposure.