EFFECTS OF DIFFERENT STYRENE METABOLITES ON CYTOTOXICITY, SISTER-CHROMATID EXCHANGES AND CELL-CYCLE KINETICS IN HUMAN WHOLE-BLOOD LYMPHOCYTES IN-VITRO

5 metabolites of styrene were tested in vitro for their cytotoxic effects, induction of SCEs and changes in cell-cycle progression in cultured human blood lymphocytes. Fresh heparinized peripheral blood (0.3 ml) from normal volunteers was cultured for a total of 72 h in 5 ml of RPMI 1640 medium containing 10% fetal calf serum, 0.1% garamycine, 1% glutamine and 1% phytohaemagglutinin. Styrene-7,8-oxide (SO), styrene glycol (SG), phenylglyoxylic acid (PGA), S-[1,2-phenyl-2-hydroxyethyl]-glutathione (PEG) (a glutathione conjugate of styrene oxide), N-acetyl-S-[1,2-phenyl-2-hydroxyethyl]-cysteine (NAPEC) in dimethyl sulfoxide (DMSO) were injected into the cultures 36 h after initial culture, so that the exposure time for these metabolites was 36 h. The final concentration of SO was 100 muM and those of the other metabolites were 500 muM. 24 h before harvest, BrdU (10 mug/ml) was added into the cultures for assessing cytogenetic endpoints. SO showed significant induction of SCEs and cell-cycle delay as well as a significant decline of cell survival. The same phenomena, but of less magnitude, were also observed with NAPEC, a cysteine derivative of SO. On the other hand, SG, PGA and PEG failed to produce any significant changes of these endpoints compared to the control. Thus, the present results have demonstrated that, in addition to SO, NAPEC possesses some cytogenotoxic potential and hence, these two metabolites together could contribute to the genotoxicity of styrene in human blood lymphocytes.