Rapid fluctuations in the levels of specific estradiol-binding sites in endometrial cells in culture.

Abstract

Levels of specific estradiol (E2) binding sites were measured during 5–6 consecutive days in primary cultures of stromal and epithelial cells from 7 specimens of human proliferative and secretory endometrium. Large day to day variations were noted, as we previously reported. Levels of binding sites were also measured hourly (1–30 h after plating) in 11 cultures of an endometrial adenocarcinoma cell line (HEC). In these experiments, striking increases and decreases were found to occur within periods as short as 2 h. The rapidity of these changes suggests reversible unmasking or activation of binding sites for E2, rather than new synthesis of binders. Elevated levels were found immediately before periods of accelerated increase in the amounts of DNA per dish, both in cultures of endometrial fibroblasts and in partially synchronized cultures of HEC cells, indicating a possible relation between levels of specific binding sites and the cell cycle. However, since elevated levels have also been found in nongrowi...