Ej. Broome et al., Adaptation of human fibroblasts to radiation alters biases in DNA repair at the chromosomal level, INT J RAD B, 75(6), 1999, pp. 681-690
Purpose: To determine whether adaptation to ionizing radiation biases repai
r of radiation-induced chromosomal breaks.
Materials and methods: Normal human fibroblasts were radiation-adapted by e
xposure to 10 cGy of gamma-radiation. FISH probes for chromosomes 2, 4, 7,
18 and 19 were used to determine the chromosomal origin of the DNA in micro
nuclei resulting from a subsequent 4-Gy exposure of these cells, and corres
ponding non-adapted cells.
Results: Compared with 4 Gy exposed but non-adapted cells, the radiation-ad
apted cells subsequently exposed to 4 Gy showed an overall decrease in the
frequency of micronuclei. However, the micronuclei that did form in the ada
pted cells had a decreased frequency of DNA originating from chromosomes 2
and 18, an increased frequency of DNA from chromosome 19 and no change in f
requency of DNA from chromosomes 4 and 7.
Conclusions: Adaptation to radiation increased the overall cellular repair
of radiation-induced chromosomal breaks, but also created a repair bias suc
h that some chromosomes were preferentially repaired or discriminated again
st, while the repair of others was unbiased.