Adaptation of human fibroblasts to radiation alters biases in DNA repair at the chromosomal level.
OBJECTIVE
To determine whether adaptation to ionizing radiation biases repair of radiation-induced chromosomal breaks.


METHODS
Normal human fibroblasts were radiation-adapted by exposure 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 micronuclei resulting from a subsequent 4Gy exposure of these cells, and corresponding non-adapted cells.


RESULTS
Compared with 4 Gy exposed but non-adapted cells, the radiation-adapted cells subsequently exposed to 4 Gy showed an overall decrease in the frequency of micronuclei. However, the micronuclei that did form in the adapted 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 frequency 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 such that some chromosomes were preferentially repaired or discriminated against, while the repair of others was unbiased.
Broome
E J
EJ
Radiation Biology and Health Physics, Atomic Energy of Canada Limited, Chalk River, Ontario.
Brown
D L
DL
Mitchel
R E
RE
D000222:Adaptation, Physiological; D002478:Cells, Cultured; D002877:Chromosomes, Human / Q000528:radiation effects*; D004249:DNA Damage; D004260:DNA Repair; D005347:Fibroblasts / Q000528:radiation effects; D006801:Humans; D008297:Male; D048629:Micronuclei, Chromosome-Defective / Q000528:radiation effects; D011829:Radiation Dosage