Suppressing effects of S phase post-treatment with carbolines on sister-chromatid exchanges induced by mitomycin C in Chinese hamster cells.

The effects of post-treatment with four types of carbolines-alpha-, beta-, gamma-, and delta-carbolines-and aminoimidazoazaarenes during S phase on the frequency of SCEs induced by MMC were studied in synchronized Chinese hamster CHO cells. Post-treatment with alpha-carbolines (A alpha C, MeA alpha C), beta-carbolines (harman, norharman, harmine, and harmaline), gamma-carbolines (Trp-P-1 and Trp-P-2) and delta-carbolines (Glu-P-1, and Glu-P-2) during S phase at non-clastogenic concentrations caused a statistically significant decrease in the frequency of SCEs induced by MMC. Aminoimidazoazaarenes (IQ, MeIQ, and diMeIQx) showed no effects on SCEs, suggesting that the SCE-suppressing activity resides in the carboline structure. The data suggest that the suppressing effect may be due to inhibition of DNA replication.