Short-term tests for transplacentally active carcinogens: sensitivity of the transplacental micronueleus test to diethylnitrosamine.

DEN is an established animal carcinogen, and is effective transplacentally; but like other nitrosamines, its genotoxicity is difficult to assess in established shortterm cytogenetic tests. The mouse transplacental micronucleus test demonstrates the ability of DEN to cause chromosome breakage in utero. Positive results were obtained from the 15th day of gestation and a linear dose-response relationship is expressed when micronucleated polychromatic erythrocytes are measured in neonatal blood, after transplacental exposure late in gestation. 25mg/kg (the lowest dose tested) caused a significant increase in MNPCEs (p less than 0.05). A micronucleus test based on polychromatic erythrocytes in neonatal blood permits maximal exploitation of the metabolic capacity of the prenatal liver and is therefore sensitive to clastogenic chemicals not activated by adult bone marrow.