MUTAGENICITY OF DIHYDROXYBENZENES AND DIHYDROXYNAPHTHALENES FOR AMES SALMONELLA TESTER STRAINS

The mutagenicity of 3 dihydroxybenzene (DHB) and 9 dihydroxynaphthalen e (DHN) isomers was examined by using 5 different Ames Salmonella muta genicity tester strains in the presence and absence of phenobarbital a nd 5,6-benzoflavone-treated rat liver SE-mix. Of the 3 DHB isomers, 1, 4-DHB (hydroquinone) was mutagenic, and of the 9 DHN isomers, 1,3-DHN (naphthoresorcinol), 1,4-DHN (hydronaphthoquinone), 1,6-DHN and 1,7-DH N were mutagenic. Mutagenicity of all the compounds tested was observe d in the absence of SE-mix, while 1,4-DHN and 1,6-DHN were also mutage nic in the presence of SE-mix. The mutagenicity of 1,4-DHB and 1,4-DHN for TA104, which is a strain sensitive to oxidative mutagens, was alm ost completely or partially inhibited by superoxide dismutase (SOD) an d/or catalase, indicating the involvement of activated oxygen species in mutagenesis. Furthermore, from the finding that the 4 DHNs were mut agenic for TA2637, the strain sensitive to frameshift mutagens, it is possible that the mutagenicity of DHNs for S. typhimurium was also att ributable to DNA adducts that form with quinones and/or semiquinones t hrough oxidation of DHNs. The mutagenicity of 1,3-DHN, which showed th e largest number of revertants in strains TA100, TA98, TA2637 and TA10 4, was greatly decreased, when their pKM101 plasmid-deficient strains, TA1535, TA1538, TA1537 and TA2659 were used. This observation suggest s that an SOS repair system was involved in the mutagenesis of 1,3-DHN for S. typhimurium.