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.
Radiation Biology and Health Physics, Atomic Energy of Canada Limited, Chalk River, Ontario.
E J
EJ
Broome
D L
DL
Brown
R E
RE
Mitchel
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