Induction of micronuclei by bleomycin in G0 human lymphocytes: I. Dose-response and distribution

The cytokinesis-block micronucleus assay was used to investigate the induction of chromosomal damage by bleomycin in G0 human lymphocytes. A dose-dependent increase in the frequency of micronuclei was observed in binucleate cells, and the frequency approached 0.5 micronuclei per cell at the highest dosage tested. The distribution of micronuclei among cells was overdispersed, rather than fitting a Poisson distribution. Even at the highest dosage, more than two-thirds of the cells did not contain micronuclei, while some cells were highly damaged, containing more than 4 micronuclei per cell.