title: A proposal for a simple way to distinguish aneugens from clastogens in the in vitro micronucleus test.
abstract: In our previous in vitro micronucleus (MN) study, we showed that aneugens, in addition to inducing micronuclei, induce a higher frequency of polynuclear (PN) and mitotic (M) cells than clastogens. We hypothesized that the frequency of PN and M cells induced can distinguish aneugens from clastogens. To test the hypothesis, we conducted the micronucleus tests with mitomycin C (MMC), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), vincristine (VINC) and diazepam in a Chinese hamster cell line (CHL) and VINC, benzo[a]pyrene (BP) and 7,12-dimethylbenz[a]anthracene (DMBA) in a subclone of V79 cells (V79-MZ). All chemicals increased the frequency of M cells with statistical significance. All chemicals except diazepam increased the frequency of PN cells with statistical significance. Three of the aneugens (VINC, BP and DMBA) induced >/=200 PN cells/1000 cells while the clastogens (MNNG and MMC) induced 100 PN cells at most. All the aneugens but no clastogens significantly increased the frequency of M cells. We propose that micronucleus test-positive chemicals that induce >/=200 PN cells/1000 cells and significantly increase the frequency of M cells are aneugens and those that induce at most 100 PN cells/1000 cells and do not significantly increase the frequency of M cells in our MN test protocol are clastogens. Diazepam, however, did not induce PN cells, although it increased the frequency of M cells dose dependently. We explain this fact in relation to diazepam's mode of action. Our proposal suggests a quick, easy and practical way to distinguish aneugens from clastogens for screening purposes.
authors.affiliation: Division of Genetics and Mutagenesis, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan. matsuoka@nihs.go.jp
authors.forename: A
authors.initials: A
authors.lastname: Matsuoka
authors.forename: K
authors.initials: K
authors.lastname: Matsuura
authors.forename: H
authors.initials: H
authors.lastname: Sakamoto
authors.forename: M
authors.initials: M
authors.lastname: Hayashi
authors.forename: T
authors.initials: T
authors.lastname: Sofuni
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000633:toxicity; D000782:Aneuploidy; D000818:Animals; D001564:Benzo(a)pyrene / Q000633:toxicity; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D003975:Diazepam / Q000633:toxicity; D008769:Methylnitronitrosoguanidine / Q000633:toxicity; D015162:Micronucleus Tests / Q000379:methods; D016685:Mitomycin / Q000633:toxicity; D009153:Mutagens / Q000633:toxicity*; D014750:Vincristine / Q000633:toxicity
chemical_list: D009153:Mutagens; D008769:Methylnitronitrosoguanidine; D001564:Benzo(a)pyrene; D016685:Mitomycin; D015127:9,10-Dimethyl-1,2-benzanthracene; D014750:Vincristine; D003975:Diazepam