Primary cultures of estrogen-responsive cells from rat uteri: induction of progesterone receptors and a secreted protein.

Uterine cells from immature rats can be grown in culture, are estrogen responsive, and contain estrogen receptors. Progesterone receptor is induced within 1 day of 17 beta-estradiol treatment, with maximal response occurring after 2 days of treatment (300-500% of the control value). Induction of progesterone receptor occurred at physiological 17 beta-estradiol concentrations, with half-maximal response at about 5 X 10(-11) M. 17 beta-Estradiol induced the synthesis of a secreted protein (mol wt, 130,000) in a dose-dependent fashion. This 130-K protein was also induced by 16 alpha-estradiol (1-10 nM), but not by progesterone (10 nM), testosterone (1 nM), or dexamethasone (1 nM). Examination of the estrogen-binding properties of the cultured cells shows a saturable binding site (Kd approximately 10(-10) M) which can be translocated to the nucleus. Estrogen receptors were maintained at in vivo levels as uterine cells proliferated throughout 10 days of culture. This was in contrast to estrogen receptor levels in Fischer 344 rat pituitary cell cultures, which dropped off drastically on a DNA basis as cells proliferated. These studies indicate that estrogen receptor-containing rat uterine cells proliferate and are responsive in primary cell cultures.