Characterization of an Estrogen-sensitive Cell Line Established from Normal Rat Endometrium

Summary The establishment of a cell line derived from endometrial tissue of a prepuberal Wistar-Furth female rat is described. The cell line U15 was established after the primary culture was grown in medium supplemented with estradiol-17β at 1 × 10 -9 m concentration. Evidence for a “transforming” role of estradiol-17β on immature endometrial cells is suspected. Clonal derivatives of this cell line produce tumors at the site of inoculation with histopathological features of adenocarcinoma of the endometrium. These tumors grow significantly better where estradiol-17β concentrations are either physiological or slightly above physiological levels (intact females and males given injections of estradiol-17β). Clonal cell lines in culture and tumors developed in situ , when injected into appropriate hosts, have shown high affinity and saturable binding proteins for estradiol-17β, estriol, and estrone, in that order of affinity. The dissociation constant (K d ) for estradiol-17β is about 2.2 × 10 -11 m, and the number of binding sites is around 6800 per viable cell in culture (6000 in the cytosol and 800 in the nuclear fraction) under the experimental conditions described. The K d for tumor preparations is about one order of magnitude higher (K d = 1.3 × 10 -10 m). Further characterization of these U15 cells is expected to help explain the mechanism of action of estradiol-17β in cloned populations of target cells in genetic terms.