T. Ikushima et al., RADIOADAPTIVE RESPONSE - EFFICIENT REPAIR OF RADIATION-INDUCED DNA-DAMAGE IN ADAPTED CELLS, Mutation research, 358(2), 1996, pp. 193-198
To verify the hypothesis that the induction of a novel, efficient repa
ir mechanism for chromosomal DNA breaks may be involved in the radioad
aptive response, the repair kinetics of DNA damage has been studied in
cultured Chinese hamster V79 cells with single-cell gel electrophores
is. The cells were adapted by priming exposure with 5 cGy of gamma-ray
s and 4-h incubation at 37 degrees C. There were no indication of any
difference in the initial yields of DNA double-strand breaks induced b
y challenging doses from non-adapted cells and from adapted cells. The
rejoining of DNA double-strand breaks was monitored over 120 min afte
r the adapted cells were challenged with 5 or 1.5 Gy, doses at the sam
e level to those used in the cytogenetical adaptive response. The rate
of DNA damage repair in adapted cells was higher than that in non-ada
pted cells, and the residual damage was less in adapted cells than in
non-adapted cells. These results indicate that the radioadaptive respo
nse may result from the induction of a novel, efficient DNA repair mec
hanism which leads to less residual damage, but not from the induction
of protective functions that reduce the initial DNA damage.