HeLa $S_3$세포에서 MMC에 의해 유발된 DNA회복합성은 농도$(0.05\sim 0.5\mu g/ml)$에 따른 증가를 보이지 않고 그 율도 비ulcorner적 낮아 $0.1\sim 0.5\mu g/ml$ 농도에서 조사한 전 세포의 $7\sim 9%$를 나타내고 있다. 시간 변화에 따른 실험에서는 MMC를 제거한 후 24시간까지 거의 비슷한 율로 DNA회복합성이 계속되고 있다. thymidine 상사체중 BUdR을 전처리한 군에서만이 MMC에 의한 DNA회복합성을 증가시켰다. 그러나 BUdR 또는 IUdR과 MMC를 복합처리 할 경우 시간경과에 따라 정상 DNA합성은 감소된다. 이들 결과는 MMC에 의해 유발된 DNA손상은 빠르고 느린 두단계로 회복됨을 암시하는 것이라 생각된다.
Dose response forDNA repair synthesis induced by various concentrations of MMC (0.05 $\sim$ 0.5 $\mu$g/ml) in HeLa $S_3$ cells was not dose-dependent and the amounts of it were relatively lower, representing $7\sim9%$ of total DNA synthesizing cells in $0.1\sim0.5 \mug/ml$ concentrations. Time dependence study showed that MMC-induced DNA repair synthesis occurred as long as for 24 hours with similar incidences in all time courses. Pretreatment with BUdR was found to have a sensitization effect on MMC-induced DNA repair synthesis, but that with IUdR was not. Combined treatment with BUdR of IUdR and MMC suppressed remarkably the semiconservative DNA synthesis especially at later time course. These results seem to suggest that damages induced in DNA by MMC might be repaired by both fast and slow excision processes.
