Simultaneous detection of chromosomal aberrations and sister-chromatid exchanges: experience with DNA intercalating agents.

Micronuclei that arise from chromosomal fragments can be used as an index of cytogenetic damage in a number of mammalian cell-culture systems. Since sister-chromatid exchanges (SCE) can be scored at the second metaphase after treatment, micronuclei that have arisen from acentric fragments at the first mitosis should be present in the same preparations. When a series of 8 mutagens, most of them intercalating agents, was studied in Chinese hamster ovary (CHO) cells, increased frequencies of micronuclei were detected at all doses which induced increased frequencies of SCE. The time required to score the slides for micronuclei was about one tenth that required for SCE. Since it is clear that aberrations and SCE have different genetic consequences and that they arise by mechanisms that differ at least in part, we find it useful to be able to measure both on the same slides. In this way mutagenic agents such as X-rays and bleomycin that produce few, if any, SCE but much chromosomal breakage would not be missed, nor would any agent that produced SCE without aberrations.