OESTROGEN CONTENT OF THE UTERINE TISSUES OF MICE AND THEIR RELATIONSHIP TO EPITHELIAL CELL PROLIFERATION AFTER SUBCUTANEOUS AND INTRALUMINAL ADMINISTRATION OF HORMONES
The oestrogen content of the separated uterine tissues (epithelium, stroma and myometrium) of mice was determined at various times between 1 and 24 h after administration of [3H]oestradiol or [3H]oestriol either subcutaneously or directly into the uterine lumen. After subcutaneous injections, the oestrogen levels of both the stroma and myometrium declined steadily from a maximum at 2–4 h after injection and more oestradiol than oestriol was always present. In contrast, the epithelium contained more oestriol than oestradiol and the levels of both hormones remained fairly constant over the period studied. However, a smaller percentage of the epithelial oestriol than of oestradiol was associated with the nuclear fraction. On the contrary, after intraluminal injections, the oestrogen content of all the separated tissues decreased from a maximum at 1–2 h and more oestradiol than oestriol was retained in all cases. A high proportion of the total epithelial content of both oestrogens was recovered in the nuclear fraction. The uterine proliferative response after intraluminal injection of oestradiol or oestriol was qualitatively and quantitatively similar to that observed after subcutaneous injection of hormone, indicating that the efficacy of the oestrogens is not markedly dependent on the route of administration. These data support current concepts of oestrogen action in the uterus but indicate that studies of the whole organ may not, in all respects, be extrapolated to the individual target tissue. The importance of nuclear hormone levels as the determinant of the oestrogenic response is also emphasized.