Comparative sensitivity of small mammals to micronucleus induction in bone marrow cells by clastogenic compounds

The bone marrow micronucleus assay is the most widely used method for detecting genetic damage in vivo, but this assay has received little attention for its possible application to biomonitoring terrestrial environments. The present study compared the responsiveness of three small mammalian species, Cryptotus parva (least shrew), Peromyscus leucopus (white-footed mouse), and strain CD-1 Mus musculus (house mouse), to the clastogen, methylmethanesulfonate (MMS). Five animals of each sex of each species were exposed for 24 h to four concentrations of MMS ranging from 0 to 50 mg/kg. Bone marrow cells were flushed from the femurs, and smears were stained with acridine orange and examined using fluorescence microscopy. The slides were scored for evidence of acute bone marrow toxicity (polychromatic to normochromatic erythrocyte ratio, PCE:NCE) and frequency of micronucleated PCE. PCE:NCE was depressed at 50 mg/kg in P. leucopus, but not in the other species. Dose-related increases in micronucleated PCE were observed in all three species, with males being more sensitive for P. leucopus and M. musculus, and females being more sensitive for C. parva. For both sexes, the two feral species, P. leucopus and C. parva, were more sensitive than M. musculus. These studies demonstrate the successful application of themore » bone marrow micronucleus assay to species other than standard laboratory strains of mice. The results also demonstrate heretofore unrecognized species differences in responsiveness.« less