Abnormalities in the reproductive system of aged mice after neonatal estradiol exposure.

Female mice of the BALB/c strain were treated neonatally with 17 beta-estradiol (E2) or sesame oil and sacrificed at 20 months of age. Neonatal treatment of mice with E2 resulted in the development of vaginal lesions, including adenosis, adenocarcinoma and squamous-cell carcinoma. While the neonatal treatment also induced squamous metaplasia in the uterine epithelium, development of uterine adenomatous hyperplasia was markedly inhibited in the estrogen-treated mice when compared to the oil-treated controls. However, neonatal exposure to E2 resulted in a high incidence of ovarian tumors and epithelial hyperplasia of the oviduct. Thus, the effects of neonatal treatment with estrogen appeared to interact with the usual effects of aging, modifying the development of pathological abnormalities in the various reproductive organs of mice.