The development of atypical epithelium in the mouse uterine cervix and vaginal fornix after neonatal oestradiol treatment.

The effect on the epithelium in the mouse uterovaginal canal of daily injections of 5 μg. oestradiol for the first 5 days after birth has been studied. Control young were injected with olive oil. The mice were followed up to 6 months after birth. The neonatal oestradiol treatment results in a strong suppression of the mitotic rate in the undifferentiated müllerian epithelium in the vaginal fornix, the uterine cervix and—after an initial stimulation—also in the uterine horns. In the vaginal fornix and the uterine cervix of animals neonatally treated with oestradiol, regions develop with an atypical epithelium—principally a columnar epithelium—instead of the normal stratified epithelium. In the uterine horns, there is a glandular hyperplasia; in the vagina, cornified epithelium. Later, the atypical epithelium forms glandular-like downgrowths into the stroma, sometimes with a diffuse border to the stroma. The atypical epithelium shows the same distribution and activity of acid and alkaline phosphatase as the uterine epithelium. The regions with atypical epithelium have the same extension after castration and a following oestradiol treatment as in animals neonatally treated with oestradiol only. The nature of the atypical epithelium and the mechanism at its development is discussed.