The effect of benzene in the micronucleus test

Abstract

The potential cytogenetic effect of benzene was studied by means of the micronucleus test in developing erythrocytes of male and female mice at dosages ranging from 0.0625 to 2.0 ml/kg/day. Groups of mice were given two daily oral doses and sacrificed 6, 18, 24 or 48 h, or 5, 9 or 16 days after the last dose. The doses were given 24 h apart. Bone marrow from the mice was processed for visualization of micronuclei in polychromatic erythrocytes. The results showed a significant ( P < 0.05) increases in the numbers of polychromatic erythrocytes with micronuclei from mice sacrificed 6 h after being given dosages of 0.25 ml/kg/day or more of benzene. Similarly, significant ( P < 0.05) increases in polychromatic erythrocytes with micronuclei were seen in mice given 0.125 ml/kg/day or more of benzene and sacrificed 18 or 24 h after the second dose. However, in a second experiment negative results were obtained at 24 h from mice at 0.0625, 0.125 and 0.25 ml/kg. One group of mice (0.25 ml/kg/day and killed at 48 h) showed significant increases in the numbers of polychromatic erythrocytes with micronuclei. Mice killed 5 days after treatment with 2 doses of 0.125 ml/kg or more of benzene showed significant numbers of micronuclei in polychromatic erythrocytes. The groups of mice at 0.5, 1.0 or 2.0 ml/kg/day and killed 9 or 16 days after the second dose of benzene showed values that were comparable to the corresponding negative controls. In all cases there were sufficient numbers of cells to analyze. Although benzene is a known hematopoietic poison and bone-marrow depressant, there were sufficient numbers of cells to evaluate in the micronucleus test. Thus, these experiments uphold the usefulness of the micronucleus test as a screening procedure in cytogenetics.