Chromosome aberrations in mouse bone marrow cells following in vivo exposure to 1,3-butadiene

Chronic exposure to 1,3-butadiene (BD) results in a marked increase in the incidence of thymic lymphoma in male B6C3F1 relative to NIH Swiss mice whereas no demonstrable differences in bone marrow (target organ) toxicity exist. Repeated exposure to BD is known to produce a macrocytic anemia and an increase in the frequency of micronuclei in circulating erythrocytes in both strains. The present study was undertaken to determine if chromosomal breakage, aneuploidy or both reflect differences in BD leukemogenicity observed between B6C3F1 and NIH Swiss mice. Mice were exposed to a single concentration of BD (1250 p.p.m.) for 6 h. Bone marrow cell preparations were made at 24, 48, 72 and 96 h after cessation of exposure. In both strains comparable increases in the frequency of chromosomal aberrations (of the chromatid type) were observed following exposure to BD. Significant differences in the number of chromosomes were not observed, although a pattern of chromosomal loss in cells from treated animals was observed. These results indicate that BD-treatment in vivo produces significant increases in chromatid aberrations but not aneuploidy in both strains. Therefore it is concluded that bone marrow toxicity, including cytogenetic abnormalities, is not predictive of leukemogenicity in these mice.