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 ce lls of mice following inhalation exposure to 1300 ppm of 1,3-butadiene (ED) for 6 h per day on 5 consecutive days, and in splenocytes of mic e 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 prese nt study, the nature of MN induced by ED, EB and DEB was analyzed by m eans of fluorescence in situ hybridization (FISH) using mouse minor sa tellite DNA and rat satellite I DNA as probes. Percentages of MN with centromere signals (MN(+)) measured following exposures to ED, EB and DEB indicate that these agents are predominantly clastogens. Frequenci es of MN(+) per 1000 cells suggest that ED, EB and DEB are not only st rong clastogens, but also weak aneugens in mice. The weak aneugenic ef fect 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 mitomyc in C (MMC) led to the following conclusions: (1) analysis of MN for th e number of centromere signals may be a useful indicator for identifyi ng chemicals with aneugenic properties; (2) there is no correlation be tween the size of MN and their origin (i.e., chromosome loss/gain or f ragment).