Feasibility of micronucleus methods for monitoring genetic damage in two feral species of small mammals.

Peromyscus leucopus (white-footed mouse) and Cryptotis parva (least shrew) possess desirable attributes for biomonitoring contamination of terrestrial ecosystems, but few studies have examined the potential use of these species for monitoring exposure to genotoxic contaminants. The susceptibility of laboratory-reared C. parva, P. leucopus, and Mus musculus (house mouse, strain CD-1) to micronucleus (MN) induction by known clastogens was evaluated. Animals were exposed for 24 hr to methyl methanesulfonate (MMS; 12.5, 25, and 50 mg/kg), 4-nitroquinoline 1-oxide (4-NQO; 7.5, 15, and 30 mg/kg), or mercuric chloride (HgCl 2 ; 6, 12, and 24 mg/kg). Both MMS and 4-NQO induced dose-related increases in micronucleated polychromatic erythrocytes (MNPCE) in all three species, whereas HgCl 2 induced a weak response only in P. leucopus. P. leucopus and C. parva were more sensitive than M. musculus to MMS. Similar micronucleus responses to 4-NQO were seen in each of the species. The feasibility of using blood for MN assessment was evaluated by comparing MN frequencies in bone marrow (BM) PCE, and blood PCE and normochromatic erythrocytes (NCE) in untreated animals, and following daily treatment for 1, 2, 3, and 10 days with 0.4 mg/kg triethylenemelamine (TEM). The results indicated that micronucleated erythrocytes were removed from the circulating blood in P. leucopus, but not in C. parva. Measurement of BM and blood MN levels appears feasible for monitoring exposure to genotoxic agents in C. parva and P. leucopus, and for distinguishing between acute and chronic exposure in C. parva.