Effects of estrogen treatment on persistent hyperplastic lesions of the vagina in neonatally estrogenized mice.

Female mice of B6AF1 hybrids (C57BL/6NXA/HeN) were treated neonatally with 5 daily injections of 20 microgram estradiol-17 beta or sesame oil from the day of birth. About half of them were ovariectomized at 40 days of age, and the other were given an implantation of an estradiol-17 beta pellet under the dorsal skin at 80 days of age. The pellet was removed 30 days later. Vaginal smear records showed persistent vaginal cornification in a number of neonatally estrogenized mice regardless of ovariectomy. When killed at 16-21 months or at 24-32 months of age, hyperplastic lesions ranging histologically from those resembling squamous cell carcinomas to adenosis-like structures were observed in neonatally estrogenized mice. The development of lesions was more pronounced in mice killed at 24-32 months of age than at 16/21 months. Secondary estrogen treatment when adults did not appreciably affect the promotion of lesions. It is therefore evident that neonatal exposure to high doses of estrogen was important primarily in connection with the neoplastic changes in the cervicovaginal tract.