Comparative studies on chromosome aberrations induced by polycyclic hydrocarbons in cell-mediated and microsome-mediated assay.

Studies were made on chromosome changes in Chinese hamster V79 cells induced by the polycyclic hydrocarbons, benzo[alpha]pyrene (BP), 3-methylchol-anthrene (MC) and 7,12-dimethylbenz[alpha]anthracene (DMBA) in the presence and absence of cell-mediated and microsome-mediated activation systems. In cell-mediated assay, BP, MC and DMBA induced concentration-dependent chromosome aberrations in V79 cells, at concentrations of 0.5--1.0 to 10.0 micrograms/ml in the presence of lethally irradiated Syrian hamster embryonal feeder cells at 2.0 X 10(6) cells/60-mm dish. The highest incidences of cells with aberrant chromosomes, observed at concentrations of 20 micrograms/ml, were 24.0% (BP), 23.0% (MC) and 80.0% (DMBA). In the absence of feeder cells, these chemicals did not induce chromosome aberrations in V79 cells, even at the maximum concentrations tested, only background levels being observed. In microsome-mediated assay, BP, MC and DMBA at 20 micrograms/ml also induced chromosome aberrations when combined with microsomes. However, the highest incidences of aberrations were observed with lower amounts of microsomes than usual, the optimal amount of microsomes ranging from 1 to 10%. In this range, the highest incidences of cells with aberrant chromosomes were 10.0% (BP), 9.0% (MC) and 28.0% (DMBA), that is about half to one-third those observed in cell-mediated assay.