Abstract
Tumorigenicity of isoniazid (INH) and hydrazine sulfate (HS) was studied in male and virgin Swiss mice. The INH and HS induced 50% und 84% lung tumors in males and 67% and 72% in females, respectively. Both chemicals induced lung tumors in animals of the F1 generation that were exposed to INH or HS during intrauterine life, lactation, and in the postweaning period. Surprisingly, the F2 generation from these F1 animals, which were exposed to INH only during gestation and lactation, showed earlier and much higher tumor incidence than the parent generation.