Clastogen-induced micronuclei in peripheral blood erythrocytes: the basis of an improved micronucleus test.

Micronuclei induced in bone marrow erythroblasts by clastogenic chemicals are easily detected in peripheral blood. In mice treated with nitrogen mustard, 7,12 dimethylbenz(a)anthracene, or cyclophosphamide, the peak incidence of micronucleated polychromatic erythrocytes in peripheral blood was at least as great as the maximum incidence in bone marrow. In each case the peak incidence in blood occurred on the day following the peak incidence observed in bone marrow. Thus, for general genetic screening purposes, monitoring micronuclei in peripheral blood rather than in bone marrow smears provides at least equal sensitivity, offers greater simplicity in sample preparation and scoring, permits multiple sampling of treated animals, and may also facilitate automated scoring and human cytogenetic monitoring.