An estradiol mitotic rate inhibiting effect in the müllerian epithelium in neonatal mice

Beginning within 24 hours after birth, young mice were given daily subcutaneous injections of 5 μg estradiol‐17β in olive oil. The mice were sacrificed at varying times; six hours before death, they were given a subcutaneous injection of colchicine. The mitotic rate was studied in the epithelium in the uterine horns, uterine cervix, and müllerian vagina. Eighteen hours after the first estradiol injection, the mitotic rate was increased in the uterine epithelium, but decreased in the cervical and müllerian vaginal epithelium compared with the controls. At a continued treatment with estradiol, the mitotic rate values decreased to a level somewhat below the control level in the uterine horns; in the uterine cervix and müllerian vagina the mitotic rate decreased to very low values, significantly lower than in the corresponding regions in the controls. The mechanisms behind this mitotic rate inhibition as well as its consequences are discussed.