Effects of postpubertal oestrogen injections on mitotic activity of vaginal and uterine epithelial cells in mice treated neonatally with oestrogen.

Cell cycles of vaginal and uterine epithelial cells were studies using [3H]thymidine autoradiography in adult ovariectomized mice given oestrogen injections neonatally. The mice were in a 'persistent-oestrous' state, showing ovary-independent, continued proliferation and cornification of the vaginal epithelium. The duration of different stages of the cell cycle could not be assessed in such mice, since the percentage of labelled mitoses failed to rise to 100%. In neonatally oestrogenized, adult mice the vaginal epithelium appeared to contain a mixed population of cells. After an oestrogen injection, almost all mitoses of vaginal epithelial cells became labelled, with a generation time of about 17 h. By contrast, the generation time was about 15 h in vaginal epithelial cells of ovariectomized 'normal' mice injected with oestrogen when adult. The uterine epithelium of neonatally oestrogenized, ovariectomized mice also consisted of a mixed population of cells. A single oestrogen injection produced an increase in both the mitotic rate and cell number in the vaginal and uterine epithelium of ovariectomized 'normal' adults but not in neonatally oestrogenized, ovariectomized adults. These studies show that in mice given oestrogen neonatally, uterine and vaginal epithelial cells were not responsive to oestrogen or at least less sensitive to oestrogen than ovariectomized 'normal' controls.