Thiopronin reduces the frequencies of neocarzinostatin-induced chromosomal aberrations and sister chromatid exchanges in Chinese hamster ovary cells

Abstract Chinese hamster ovary (CHO) cells were treated in the G 1 phase of the cell cycle with different concentrations of neocarzinostatin (NCS) alone or in combination with N -(2-mercaptopropionyl)-glycine (thiopronin; TP). TP reduces the frequencies of NCS-induced chromosomal aberrations (CA) and of sister chromatid exchanges (SCE) significantly when added to the cultures simultaneously (TP sim ), 1 min (TP 1 ) or 10 min (TP 10 ) after the addition of NCS. The addition of TP 30 min (TP 30 ) or 60 min (TP 60 ) after NCS reduces the frequencies of SCE, but not of CA. Our results indicate that the induction of CA and SCE by NCS is partially based on different mechanisms.