This study was conducted to evaluate the potential of 4-vinylcyclohexene (V
CH) to induce micronuclei in the bone marrow of mice and rats. Male and fem
ale Crl:CD BR (Sprague-Dawley) rats and B6C3F1/CrBR mice were exposed to VC
H 6 hr/day for 2 days or for 13 weeks. In the 2-day study, mice were expose
d by inhalation to 0, 250, 500, or 1000 ppm. and rats were exposed to 0, 50
0, 1000, or 2000 ppm. In the 13-week study. mice were exposed to 0, 50, 250
, or 1000 ppm, and rats were exposed to 0, 250, 1000, or 1500 ppm. In each
study, a separate group of mice was exposed to 1000 ppm 1,3-butadiene (BD)
so that a comparison could be made between the two compounds. Likewise, cyc
lophosphamide was also included for rats as a positive control. Bone marrow
was collected from VCH-exposed animals approximately 24 h and 48 h after t
he final exposure. There were no statistically significant increases in mic
ronucleated-polychromatic erythrocytes (MN-PCEs) among VCH-treated mice and
rats at any dose level or sampling interval at either 2-days or 13-weeks.
Also, no statistically significant differences in the polychromatic erythro
cytes (PCE) to normochromatic erythrocytes (NCE) ratios were observed in an
y of the VCH-treated mice and rats compared to air-exposed animals. As expe
cted, both the butadiene-treated mice and the cyclophosphamide-treated rats
showed significantly more MN-PCEs than the control animals.