Augmentation of the response of mouse uterine epithelial cells to estradiol by uterine stroma.

The effect of estrogen on the in vitro growth of mouse uterine epithelial cells was assessed. Epithelial cells from the immature mouse uterus were successfully cultivated in a 1:1 mixture of Dulbecco's Modified Eagle's Medium and Ham's F-12 supplemented with insulin (5 micrograms/ml), transferrin (10 micrograms/ml), hydrocortisone (10(-7) M), BSA (2 mg/ml), and fetuin (1 mg/ml). Addition of 17 beta-estradiol in the range of 1-100 nM did not significantly change the total DNA content of the epithelial cells. A binding component of [3H]estradiol by cultured uterine cells was shown to be specific, saturable, and of high affinity. Kd values for specific binding by epithelial and stromal cells were 1.0-1.7 x 10(-10) M. Maximal specific binding was 0.74 and 2.3 fmol/micrograms DNA for epithelial and stromal cells, respectively. Treatment of epithelial and stromal cells for 4 days with 10 nM estradiol led to a 2- to 6-fold increase in progesterone receptor concentration. Treatment of epithelial and stromal cells in mixed culture for 4 days with 10 nM estradiol resulted in a significant increase in total DNA. That epithelial-stromal contact was critical for estradiol stimulation was shown by the fact that if the cell types were separated into two compartments which still allowed free media mixing, total DNA was not enhanced by estradiol. These observations are organized into a model for mitogenic action of estradiol that seems to reconcile observed disparities in the action of the hormone in vivo and in vitro.