PLASMA-MEMBRANE IS THE PRIMARY SITE OF LOCALIZATION OF THE NONACTIVATED ESTROGEN-RECEPTOR IN THE GOAT UTERUS - HORMONE-BINDING CAUSES RECEPTOR INTERNALIZATION

Evidence is presented to show that the cellular site of localization o f the goat uterine nonactivated estrogen receptor (naER) is the plasma membrane. Exposure of purified plasma membrane preparations to estrad iol (20 nM) causes dissociation of the receptor from the membrane into the medium. This receptor movement takes place in the presence of die thylstilbestrol while testosterone, progesterone, dexamethasone, and t amoxifen do not facilitate the dissociation of the naER from the plasm a membrane. Further, tamoxifen inhibits the estradiol-mediated dissoci ation of the naER from the plasma membrane. The naER is a glycoprotein and is also a tyrosine kinase. The tyrosine kinase activity is inhibi ted in the presence of estrogens while tamoxifen reverses this estroge n-dependent inhibition. (C) 1996 Academic Press, Inc.