DOSE-DEPENDENT GENOTOXIC EFFECTS OF STYRENE ON HUMAN BLOOD-LYMPHOCYTES AND THE RELATIONSHIP TO ITS OXIDATIVE AND METABOLIC EFFECTS

Although the genotoxic potential of styrene is known, very limited inf ormation is available regarding its dose-dependent genotoxic response to human blood lymphocytes and how such response correlates with diffe rent metabolic events in whole blood lymphocytes. The present study wa s therefore carried out to study such a relationship using in vitro hu man blood lymphocytes from healthy volunteers. To study genotoxic resp onse to styrene, sister chromatid exchanges (SCEs), cell cycle, and ce ll survival were analyzed. Lymphocytes were cultured for 72 hr in the presence of different concentrations of styrene (0-1,000 muM). Twenty- four hr before harvest, BrdU (5 mug/ml) was added to assess the increa se in SCEs and cell cycle delay. Both the SCE frequency and the cell c ycle length were increased linearly with increasing concentrations of styrene up to 200 muM, without addition of any exogenous metabolizing system. Above 200 muM, no further increase in genotoxic response occur ed. The range of -concentrations (10-200 muM) at which increase,of cel l cycle length due to styrene was observed did not impair the viabilit y of the cells, suggesting that such cell cycle delay is a genotoxic-r elated event and not caused by cytotoxicity. In vitro metabolic transf ormation of styrene in whole-blood lymphocyte cultures without the pre sence of any exogenous metabolic activation system showed the formatio n of a reactive intermediate, styrene 7,8-oxide, to be capacity-limite d, as verified from a nonlinear increase in the formation of styrene g lycol. The value of such metabolic parameter reached a plateau above 2 00 muM styrene. The same phenomenon of saturation has also been observ ed with regard to other metabolic effects due to styrene in whole bloo d lymphocytes in culture, such as dose-dependent increase in lipid per oxidation and depletion of blood lymphocyte glutathione. Based on the relationship between the formation of different metabolic events and t he genotoxicity of styrene, it may be possible that the genotoxic prop erties of styrene in human blood lymphocytes may be mediated initially not only by the formation of the presumably reactive styrene 7,8-oxid e, but also by that of a reactive oxygen species as well. However, the present data are not sufficient enough to definitely identify the rol e of reactive oxygen species in such toxicity and therefore it warrant s further study. (C) 1993 Wiley-Liss, Inc.