title: Induction of micronuclei and anaphase aberrations by cytochalasin B in human lymphocyte cultures.
abstract: The frequency of micronucleated cells in isolated 72-h human lymphocyte cultures treated with cytochalasin B (Cyt-B; 1.5-6 micrograms/ml for the last 28 h) was 9-21 times higher (mean 14.6 times) among multinucleate than binucleate cells. At 3 micrograms/ml, the concentration of Cyt-B originally recommended for the human lymphocyte micronucleus assay, the frequency of micronucleated multinucleate cells was 8.5%, while 0.7% of the binucleate cells had a micronucleus. Although no dose-dependent induction of micronuclei could be observed for either of the cell types, increase in the concentration of Cyt-B was associated with a decrease in the ratio of multinucleate to binucleate cells. Treatment with Cyt-B (1.5-12 micrograms/ml) increased the frequency of anaphase cells with aberrations, especially lagging chromatids. This finding was explained by a dose-dependent increase in multipolar (greater than or equal to 3 poles) divisions which had a high frequency of anaphase aberrations (39-53%), irrespective of the concentration of Cyt-B. Bipolar anaphases did not show a significant increase in aberrant cells, although a suggestive dependence on the concentration of Cyt-B was observed. The findings indicate that the high frequency of micronuclei in multinucleate lymphocytes produced by Cyt-B is due to mitotic errors arising when bi- (and multi-) nuclear cells divide. To avoid possible artifactually high micronucleus frequencies due to inclusion of cells that have divided greater than or equal to 2 times in the presence of Cyt-B, it is recommended that, in the human lymphocyte micronucleus assay using the cytokinesis-block method, the cell culture time is reduced to minimize the frequency of such cells and that only good preparations and regularly shaped binucleates are included in the analysis.
authors.affiliation: Department of Industrial Hygiene and Toxicology, Institute of Occupational Health, Helsinki, Finland.
authors.forename: C
authors.initials: C
authors.lastname: Lindholm
authors.forename: H
authors.initials: H
authors.lastname: Norppa
authors.forename: M
authors.initials: M
authors.lastname: Hayashi
authors.forename: M
authors.initials: M
authors.lastname: Sorsa
mesh_terms: D000328:Adult; D000705:Anaphase; D002478:Cells, Cultured; D002869:Chromosome Aberrations; D003571:Cytochalasin B / Q000633:toxicity*; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects*; D008297:Male; D015162:Micronucleus Tests; D009153:Mutagens
chemical_list: D009153:Mutagens; D003571:Cytochalasin B