Inhibition of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline-mediated DNA-adduct formation by chlorophyllin in Drosophila.

The effect of chlorophyllin on 2-amino-3,8-dimethyimidazo[4,5-f]quinoxaline (MeIQx)-mediated DNA-adduct formation in Drosophila was studied. Third-instar larvae of Drosophila were fed MeIQx at 1 mg/6.5 g-feed/bottle, with or without chlorophyllin (100-300 mg). After a 6 h feeding exposure to MeIQx, the larvae were divided into 2 groups. The first group was examined for covalent DNA adducts by 32P-postlabeling assay. The second group was assayed for DNA damage by allowing the larvae to develop to adults and measuring the male/female ratio (males, DNA repair-deficient; females, DNA repair-proficient). The 32 P-postlabeling results indicated a significant decrease in DNA adduct levels in larvae treated with MeIQx and 300 mg chlorophyllin (1.7 +/- 0.7 adducts/10(7) nucleotides) as compared with MeIQx-treated larvae 6.5 +/- 2.1 adducts/10(7) nucleotides). The results on male/female sex ratios also indicated a chlorophyllin-induced decrease in DNA damage by exposure to MeIQx. The suppressive effect of chlorophyllin on the genotoxic actions of a polycyclic mutagen, MeIQx, may be a result of complex formation between chlorophyllin and the mutagen.