OBJECTIVETo investigate DNA repair in CHL cells and HeLa cells after DNA damage induced by different oxidative agents.

METHODSCHL cells and HeLa cells were exposed to various damaging agents, CHL cells: H(2)O(2) for 25 min, K(2)Cr(2)O(7) for 105 min, doxorubicin (Dox) for 75 min HeLa cells: H(2)O(2) for 25 min, K(2)Cr(2)O(7) for 105 min; then cells were continuously cultured for 0-3 h after washing. Alkaline single cell gel electrophoresis (ASCGE) assay was used to detect DNA strand breaks.

RESULT(1) DNA strand breaks were induced in CHL cells after exposure to H(2)O(2) K(2)Cr(2)O(7) or Dox, which were repaired evidently after continuous culture for 1 h(P<0.01). The damages induced by H(2)O(2) or K(2)Cr(2)O(7) were repaired completely after culture for 2-3 h. However, the demage induced by Dox was repaired incompletely. (2) DNA strand breaks were induced also in HeLa cells after exposure to H(2)O(2) or K(2)Cr(2)O(7), which were repaired evidently after continuous culture for 0.5 h(P<0.01),and completely after culture for 1 h. (3) The regression coefficient related to the rate of comet cells and repair time was statistically different (P<0.05) between CHL cells and HeLa cells.

CONCLUSIONDNA damage induced by Dox is repaired more difficult than that induced by H(2)O(2) or K(2)Cr(2)O(7). The repair initiates immediately after DNA damage in both of cells, but more rapidly in HeLa cells than in CHL cells.