The effects of microsomal activation and/or deactivation on the induction of
chromosomal aberrations and sister-chromatid exchanges (SCEs) in cultured Chinese hamster ovary cells (CHO-K1 cells) by
o-phenylphenol (
OPP) were studied, and concurrently the metabolites were determined. After a 3-h incubation in the presence of 15% S9 mix (45 microliters/ml of S9),
OPP (25-150 micrograms/ml) dose-independent SCEs and
chromosomal aberrations were induced, while the amount of
phenylhydroquinone (PHQ) metabolite produced from
OPP did not increase linearly in the higher doses. The maximum induction of
chromosomal aberrations was 18% at the 150 micrograms/ml dose, and of SCEs 13.8/cell at 75 micrograms/ml. The corresponding control values were 3% and 5.8/cell. The lowest dose required to induce SCEs in the presence of S9 mix was 25 micrograms/ml. Changing the percent of S9 mix (0-50%) while holding the
OPP dose constant (100 micrograms/ml) produced a correlation between SCEs and the production of PHQ. PHQ caused cytogenetic effects both with and without S9 mix, however, in the absence of S9 mix it was more lethal and was oxidized to
phenylbenzoquinone (PBQ). These results suggest that the enhanced cytogenetic effects of
OPP by the addition of S9 mix correlated with the amount of PHQ produced or with the further
oxides of PHQ such as phenylsemiquinone and/or PBQ which are capable of being produced from PHQ spontaneously or by the
mixed-function oxidase system.