Mouse spot tests with alkylnitrosoureas.

Spot tests with various alkylnitrosoureas were carried out using the newly established PW strain of male and female C57BL/6 mice. Chemicals tested were N-methyl-N-nitrosourea (MNU), N-ethyl-N-nitrosourea (ENU), N-propyl-N-nitrosourea (PNU) and N-butyl-N-nitrosourea (BNU). Although MNU had a severe teratogenic effect, no clearly positive color spot was obtained, while apparent induction of their color spots was observed with ENU, PNU and BNU. The frequency of appearance of these color spots was dose-dependent. In F1 males from the treated group, the weight of the testes was significantly lower in mice about 30 days old. It is suggested that these chemicals may have mutagenic effects on both developing somatic and germ cells of mice.