Induction of sister-chromatid exchanges in human lymphocytes by indirect carcinogens with and without metabolic...

Sister-chromatid exchanges (SCEs) were examined in cultured human lymphocytes after exposure for 1 h to aflatoxin B1 (AFB1), Trp-P-1, Trp-P-2, dimethyl-nitrosamine (DMN), diethylnitrosamine (DEN) and benzo[a]pyrene (BP) with and without a metabolic activation system (S9 mix). With metabolic activation, all the carcinogens produced significant and dose-dependent increases in SCE frequency. However, the molar concentrations that induced a 2-fold increase in SCEs per cell over the control level were distributed over a range of more than 10(4). Without metabolic activation, AFB1, at 10(-4) M, caused a significant increase in SCE induction, whereas the other compounds caused little or no increase in SCE frequency above the control levels.