MORPHOLOGY AND ORIGIN OF MICRONUCLEI INDU CED BY MITOTIC INHIBITORS

In order to elucidate the morphological variation and the origin of er ythrocytic micronuclei induced by mitotic inhibitors, each of clastoge ns (mitomycin C and cyclophosphamide) and spindle poisons (vincristine and colchicine) was administered intraperitoneally into a rat. After 24 h, the bone marrow smear was prepared and subjected to the microsco pic analysis. In consequence, the sizes of micronuclei (MNSs) induced by spindle poisons were generally larger than those (MNCs) induced by clastogens. On the other hand, the bone marrow cells containing micron ucleated erythrocytes were fractionated by cellulose column chromatogr aphy and then Percoll-gradient centrifugation. The micronuclear DNA wa s extracted from the resulting erythrocyte fraction and subjected to t he dot blot hybridization with a centromeric or telomeric DNA probe. T his experiment showed that centromeric and/or telomeric DNAs are enric hed more in MNSs than in MNCs. Thus, such hybridization techniques and the morphological analysis would be available for classifying micronu cleus-inducing drugs.