Analysis of micronuclei induced by 1,3-butadiene and its metabolites using fluorescence in situ hybridization

In our previous study, micronuclei (MN) were induced in bone marrow cells of mice following inhalation exposure to 1300 ppm of 1,3-butadiene (BD) for 6 h per day on 5 consecutive days, and in splenocytes of mice and rats treated intraperitoneally with 80 mg/kg 1,2-epoxybutene (EB) and 30 mg/kg 1,2,3,4-diepoxybutane (DEB), respectively. In the present study, the nature of MN induced by BD, EB and DEB was analyzed by means of fluorescence in situ hybridization (FISH) using mouse minor satellite DNA and rat satellite I DNA as probes. Percentages of MN with centromere signals (MN+) measured following exposures to BD, EB and DEB indicate that these agents are predominantly clastogens. Frequencies of MN+ per 1000 cells suggest that BD, EB and DEB are not only strong clastogens, but also weak aneugens in mice. The weak aneugenic effect of EB and DEB was not observed in rats. Analysis of the number of centromere signals in individual MN, and the size distribution of MN with centromere signals in EB- and DEB-treated animals, and in animals exposed to the positive controls diethylstilbestrol (DES) and mitomycin C (MMC) led to the following conclusions: (1) analysis of MN for the number of centromere signals may be a useful indicator for identifying chemicals with aneugenic properties; (2) there is no correlation between the size of MN and their origin (i.e., chromosome loss/gain or fragment).