Control of uterine stromal mitosis in relation to uterine sensitivity and decidualization in mice

The relationship between mitosis, ovarian hormones, decidual stimuli and decidualization was investigated using progestagen-treated ovariectomized mice. Oestradiol, or the intraluminal instillation of oil or saline, all stimulated stromal mitosis. When oil or saline was instilled following oestradiol, the response depended on the dose of oestradiol, the interval between the oestradiol and the instillation, and the time when the mice were killed. After 20 ng oestradiol, the instillation of oil 7 h later induced large mitotic and decidual responses that were evident within 17 h of instillation and increased with time. Smaller mitotic and decidual responses were obtained when the interval between oestradiol and oil was 24 h; there was no response when the interval was 42 h. When a higher dose (100 ng) of oestradiol was given, oil injected 7 h later initially stimulated mitosis (at 17 h), but this effect was reduced at 24 h and no decidualization occurred. After instilling oil 24 or 42 h after 100 ng oestradiol, the mitotic response was limited, and there was no decidual response. Regardless of the dose of oestradiol, saline induced only a transient mitotic response and no decidualization occurred. It is concluded that there are three stimuli that can cause stromal mitosis in the progestagen-treated mouse uterus: oestrogen, an intraluminal stimulus (blastocyst, oil or saline) and factors associated with decidualization. Oestradiol not only induces mitosis, but also produces a period of heightened sensitivity to the mitotic effects of intraluminal stimuli. In addition, low doses of oestradiol induce a period of sensitivity to decidual stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)