Kinetic analysis of hormone-induced mitoses in epithelial cells of mouse uterus and vagina.

The intracellular localization of 3H-estradiol-17beta and 3H-progesterone to the different types of cells in the mouse uterus was investigated using autoradiographic techniques. The kinetics of cell proliferation in the surface epithelium of the uterus and in the vaginal epithelium (basal layer) are analysed by means of cumulative labeling method and mitosis chase method using 3H-thymidine autoradiographic procedures. The results are as follows, (1) Epithelial cell population of the uterine lumen and basal cell population of the vaginal epithelium in the ovariectomized mouse are divided into a major subpopulation of GO cells and a minor subpopulation of proliferating cells. (2) Proliferative potencies of uterine surface epithelial cells and vaginal basal cells in the ovariectomized mouse are regulated by a steroid-independent mechanisms through which the proportion of the GO cell-compartment and Tc value of the proliferating cell-compartment are determined according to their age; as the castrated mouse grows older, Tc value becomes longer and the proportion of the Go cell-compartment becomes larger. (3) If the dose levels of estrogen administered exceed the threshold value, estrogen-dependent cell proliferation will be provoked by transferring the cells in the GO cell-compartment to the proliferating cell-compartment in all or none fashion, and by reducing the Tc value of proliferating cell to 1/2-1/3 of that in the castrated mouse. (4) It is suggested that proliferating cells in the uterine surface epithelium and in the vaginal epithelium turn the cell cycle at a constant Tc value during estrous cycle, and that the tissue growth during estrous cycle is dependent on the size of the proliferating cell-compartment but not on the Tc value. (5) The results obtained from autoradiography of tritiated steroids in the mouse uterus gave a supporting clue to the kinetic data.