Failure to transmit diethylnitrosamine tumorigenicity from transplacentally exposed F1 generation Syrian hamsters to the respiratory tract of F2 and F3 generations

A multigeneration study with four successive generations of Syrian hamsters was conducted to determine whether a single s.c. injection of different doses of diethylnitrosamine (DEN) (1.25,2.5,5,10, and 20mg/kg body weight) on day 15 of pregnancy induces respiratory tract tumors not only in the treated P generation mothers and their F1 progeny but also F2 and F3 generations. In this study, the P generation mothers only were given a single injection of DEN during the period of gestation. Fifty-six % of the 36 DEN-treated mothers and 52% of their F1 generation offspring (total, 233 animals) developed neoplasms in the respiratory tract. A single respiratory tract tumor was found in one DEN-unexposed F1 generation control hamster as well as in one F2 generation animal (total, 209 animals) descended from DEN-exposed P generation. Both tumors were considered to have arisen spontaneously. No respiratory tract tumors were observed in the F3 generation (total, 160 animals) descended from DEN-exp osed P generation. Thus our results indicate that the vertical transmission of the tumorigenic effect of DEN in Syrian hamsters is limited to one generation and does not persist in the F2 and F3 generations