Nuclear concentration of estriol in superfused human endometrium; competition with estradiol |
| |
Authors: | L Tseng E Gurpide |
| |
Affiliation: | Departments of Obstetrics and Gynecology and of Biochemistry, Mount Sinai School of Medicine (CUNY), New York, New York 10029, U.S.A. |
| |
Abstract: | Human endometrial slices were superfused with tritiated estriol (E3). No metabolism of E3 was noted. The ratio of concentrations of the hormone in tissue and superfusion medium (T/M)E3 was found to be approximately 4. When the concentrations of [3H]-E3 in the medium were increased from 18 to 700 ng/ml. the intracellular concentrations of E3 were proportionally elevated. However, the level of E3 tightly bound to nuclei reached a maximum value. This value was equivalent to the saturation level of nuclear bound estradiol (E2) obtained when another portion of the same tissue was superfused with excess E2. Competition of E3 and E2 for nuclear binding was observed when tissue slices were superfused with mixtures of the two tritiated steroids. The nuclear E2 displaced was stoichiometrically replaced by E3, likely as a result of competition for the same binding sites of the receptor in the nucleus. A 50% displacement of E2 from the receptor in the nucleus was achieved when the ratio of intracellular concentrations of E3 and E2 was about 2. Calculations are presented to show that this ratio corresponds to the relative association constants of the E2- and E3-receptor complexes in the nucleus. |
| |
Keywords: | |
本文献已被 ScienceDirect 等数据库收录! |
|