Expulsion of demecolcine-induced micronuclei from mouse bone marrow polychromatic erythrocytes.

The mouse micronucleus test is a valuable tool for evaluating in vivo chromosome damage produced by test articles in polychromatic erythrocytes of bone marrow. Compounds that are clastogens, such as cyclophosphamide, induce micronuclei that are smaller than those induced by compounds that are spindle poisons, such as demecolcine. In vitro studies have previously shown that the frequency of mitomycin C- and vincristine-induced micronuclei in mouse L-929 cells was reduced due to micronuclear extrusion following treatment with cytochalasin B. The current study shows that micronuclei are also expelled in vivo, that expulsion is dependent upon micronuclear size, and that observation of these extruded micronuclei is dependent upon the method of sample preparation.