Increased Incidence of Tumors in F1 and F2 Generations from Pregnant Mice Injected with a Polycyclic Hydrocarbon. ∗

Summary

Pregnant Swiss mice were injected i.p. with 500 or 350 γ of 7,12-dimethylbenz(a)anthracene (DMBA) in tri-n-caprylin. Delivery occurred between 12 hours and 7 days after the injection. Five females, descendants from 2 pregnant mice injected with 350 γ of DMBA, were mated with their brothers. In both F1 and F2 untreated descendants a high incidence of tumors occurring at various sites was recorded. The most frequently occurring tumors were mammary carcinomas, granulosa cell tumors of the ovary and lung adenomas in the females, and lung adenomas, adenomas and carcinomas of the paraurethral gland in males. Many of the tumor-bearing animals bore more than one tumor. The transmission of the carcinogen via the mother's milk probably occurs in the mice of the F1 generation. The enhancement of an inherited low susceptibility to certain tumors seems to be the cause for the high incidence of tumors in the mice of the F2 generation.