ESTROGEN-BINDING PROTEINS IN THE HUMAN POST-MENOPAUSAL UTERUS

Two intracellular high-affinity, low-capacity estrogen-binding proteins, which have the characteristics of receptors, with equilibrium dissociation constants of 10-10M and 10-9M, have been observed in the human uterus. The higher-affinity protein (10-10M) appears to play the main role in activating end-organ response to estrogen stimulation. The role of the lower-affinity protein (10-9M) is uncertain. In a human postmenopausal uterine system without estrogen stimulation, Scatchard analysis of uterine cytosol partially purified by ammonium sulfate fractionation and incubated at 4° C for 18 hours revealed only the higher-affinity receptor component (10-10M). In a postmenopausal uterine system with estrogen priming (and in the premenopausal uterus) both the high- and low-affinity components were observed. Competition studies indicated that the receptors were specific for estradiol. The clinical significance of these findings is discussed. © 1979.