DNA-DAMAGE IN ISOLATED RAT HEPATOCYTES EXPOSED TO CI PIGMENT ORANGE-5AND CI PIGMENT YELLOW-12 BY THE ALKALINE COMET ASSAY

The induction of DNA damage by commonly used printing ink pigments, C. I. pigment orange 5 (C.I. 12075) and C.I. pigment yellow 12 (C.I. 2109 0), was investigated in freshly isolated rat hepatocytes with the come t assay. C.I. pigment yellow 12 is a 3,3'-dichlorobenzidine-based diar ylide pigment, and C.I. pigment orange 5 is a naphthol-azo pigment. Th e pigments are virtually insoluble in aqueous solutions, and they have not been tested extensively for toxicological effects. C.I. pigment o range 5 increased the levels of DNA damage at 5 mu g/ml (P < 0.02) and C.I. pigment yellow 12 at 20 mu g/ml (P < 0.002). The effect of incub ation time (20, 40, and 80 min) of the same concentrations of the pigm ents was tested. The levels of DNA damage were increased up to 80 min. Both pigments produced DNA damage that was in the same range as the f ood carcinogen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline. Our data indicate that both C.I. pigment orange 5 and C.I. pigment yellow 12 a re genotoxic in hepatocytes with metabolizing capacities. However, fur ther investigation of the metabolism and disposition are required for the evaluation of the safety of these pigments. (C) 1998 Wiley-Liss, I nc.