Effects of prenatal treatment with estrogen on mitotic activity of vaginal anlage cells in mice.

Abstract

Female fetuses of C57BL/Tw mice were injected s.c. with 50 .mu.g 17.beta.-estradiol on day 17 of fetal life. The treatment induced ovary-independent proliferation and cornification in the vaginal epithelium in later postnatal life. These fetuses were sacrificed on day 19 or 20, or on the 3rd day after birth. Histological observation on day 19 or 20 of fetal life did not show a particular effect of estrogen at any portion of the vaginal anlage; however, but at 3 days after birth, the epithelium of the Muellerian vagina in estrogen-treated females consisted of a single layer of columnar cells, whereas that in controls had double-layered columnar cells. A study of the mitotic rate revealed that the epithelial cells on the Muellerian vagina, and those of the cervix, were dividing more actively in fetuses than in pups. Estrogen injection on day 17 induced a marked suppression of the mitotic rate in the epithelium of the Muellerian vagina and cervix on day 19 and 20. Estrogen treatment caused a significant increase in the mitotic rate of the epithelium of the sinus vagina, at least on days 19 and 20. The epithelial cells of the sinus vagina evidently respond positively to estrogen and, thus, possibly play the main role in the development of irreversible changes in the vagina.