The size of cytokinesis-blocked micronuclei in human peripheral blood lymphocytes as a measure of aneuploidy induction by Set A compounds in the EEC trial.

We have investigated the potential value of estimating number and size of micronuclei in cytokinesis-blocked human peripheral blood lymphocytes as a measure of the aneuploidy-inducing ability of 5 chemicals in the EEC trial. Colchicine induced metaphase arrest, high numbers of cells with micronuclei and also of cells with completely fragmented nuclei. The majority of micronuclei were very significantly larger in relation to the main nucleus than a comparable set taken from untreated control cultures. In the same assay system, diazepam weakly increased the incidence of MN in a dose-related fashion. There was a slight increase in MN but only at toxic doses when cells were treated with econidazole, chloral hydrate or hydroquinone. For each of these 4 drugs, statistical treatment of the data confirmed a difference in size distribution of the MN as compared to those found in negative control cultures. Although this approach has potential, it may not be optimal to detect weak aneuploidy-inducing agents.