Significance of the Proportion of Binucleate Cells in the Micronucleus Assay

Using treatment with cytochalasin-B (Cyt-B) for the induction of a cytokinetic block, the significance of the proportion of binucleate cells (BNC) in the micronucleus (MN) assay was investigated in a methodological study. A Chinese hamster cell line V79 was used in which MN were induced by radiation. In complementary tests the radiation effect in inducing MN was enhanced by depletion of the cellular glutathione content with buthionine sulfoximine (BSO). The data indicated that the concentration of Cyt-B is the major factor which determines the proportion of BNC. This proportion was shown to be independent of radiation dose and of BSO. Furthermore, the MN frequency was not related to the percentage of BNC. Therefore, a high proportion of BNC may be practical for the MN assay, but may not make the technique more accurate.