Mutations induced in male germ cells after treatment of transgenic mice with ethylnitrosourea

The present study was undertaken to clarify whether the transgenic mouse mutagenesis assay system can be used instead of dominant lethals or specific locus test after treatment of male germ cells in mouse with ethylnitrosourea (ENU). Male Big Blue transgenic mice (BB) carrying a lacI target gene were given a single intraperitoneal injection of 150 mg/kg ENU. Vasa deferential sperm, caudal epididymal sperm or whole testes were assayed for mutation at 3, 14, 22 and 93 days after treatment with ENU. The average of background lacI- mutant frequencies was 2.05 x 10(-5). The MF observed in post spermatogonial stage after treatment with ENU were slightly increased over background. On the other hand, ENU induced high MF in the spermatogonial stage. MF detected after treatment of BB male germ cells with ENU were lower than those detected in the mouse visible specific-locus mutations in previous reports. Nevertheless, it is clear that this assay is a practical alternative to the specific locus test for detecting mutations induced in spermatogonial stage.