Estradiol entry into endometrial cells in suspension

Abstract

Cells from a human endometrial adenocarcinoma cell line (HEC-50) were superfused with mixtures of [ 3H]E 2 and [ 14C]E 1 in order to estimate rates of entry and exit of E 1 and E 2 into and out of cells accorcling to previously published procedures ( J. steroid Biochem., 13 (1980) 1379). Proportionality between rates of entry and concentrations of E 2 outside the cells, indicative of passive diffusion, was found at levels of E 2 ranging from 1 to 100 ng/ml. Effects of albumin and of pure human sex steroid binding protein (SBP) on the rate of entry of E 2 were also evaluated in parallel superfusions. In other single tracer experiments, [ 3H]E 2 was used at concentrations as low as 100pg/ml and the effects of plasma proteins on entry were evaluated by measuring steady-state concentrations of E 2 and E 1 in cells and superfusate. Results from these experiments indicate that albumin, and to a larger extent SBP, reduced the entry of E 2 into HEC-50 cells. Similar results were obtained when CG-5 cells, a variant of the human breast cancer cell line MCF-7, were superfused with [ 3H]E 2. Further experiments are needed, however, to determine the physiologic role of plasma estrogen binding proteins on the entry and metabolism of E 1 and E 2 into target cells.