DNA repair synthesis induced by azo dyes in primary rat hepatocyte cultures using the bromodeoxyuridine density-shift method.

The genotoxic activity of the benzeneamine-derived azo dyes, Disperse Red 54 (DR 54), Direct Red 81 (DR 81) and Direct Black 19:1 (DB 19:1) was studied in the in vitro DNA repair assay in primary rat hepatocyte cultures. Hepatocytes were isolated, cultured and treated with the azo dyes, bromodeoxyuridine and [3H] cytidine. DNA repair synthesis was determined as an incorporation of [3H] cytidine into unreplicated DNA strands using the bromodeoxyuridine density-shift method. Of the 3 azo dyes, only DR54 (monoazo dye) induced a weak DNA repair synthesis in rat hepatocytes in vitro. DR81 and DB 19:1 did not induce any concentration-related DNA repair synthesis expressed as cpm/micrograms DNA. The data suggest that the in vivo reduction of azo dyes is required for the genotoxicity of these azo dyes.