Comparison of different methods for an accurate assessment of cytotoxicity in the in vitro micronucleus test without cytokinesis block.

A European collaborative study was conducted in order to investigate the different measurements of cytotoxicity assessment in the in vitro micronucleus test. Relative population doubling and relative increase in cell counts were the measurements of cytotoxicity assessed in this study. The test chemicals, etoposide, benzo[a]pyrene, cytosine arabinoside and diethylstilboestrol were tested in this in vitro micronucleus assay, in mouse lymphoma L5178Y cells, without cytokinesis block. This study was conducted in support of the toxicity measurements recommended in the draft OECD Test Guideline 487. Etoposide, benzo[a]pyrene and cytosine arabinoside produced positive responses at concentrations where approximately 50% toxicity was observed measured by relative population doubling and relative increase in cell counts. Diethylstilboestrol was negative at all concentrations tested. These results are in concordance with the principles of the draft OECD Test Guideline 487.