The induction of DNA strand breaks and formation of semiquinone radicals by metabolites of 2,4,5-trichlorophenol.

The industrial pollutant 2,4,5-trichlorophenol (2,4,5-TCP) was metabolized with postmitochondrial liver fraction from Aroclor-1254 induced rats. The generated metabolites induced single strand breaks in PM2 DNA. Among the metabolites produced are the 3,4,6-trichlorocatechol (TCC) and the 2,5-dichlorohydro-quinone (DCH), whereby the induction of DNA scission by DCH was approximately one hundred times greater than that of TCC. In the 2,4,5-TCP metabolization mixture radicals were observed by ESR. They were identified as the semiquinones of TCC and DCH. ESR studies confirmed that both TCC and DCH autoxidize in aqueous solution to their semiquinone radicals. The involvement of reactive oxygen species in the DNA strand scission was demonstrated by using DMSO, SOD, and catalase as scavengers. Inhibition of strand breaks with the scavenger enzymes did not give homogeneous results for DCH and TCC. This indicated that the directly damaging species might be different for DCH and TCC.