THE OTHER ESTROGEN-RECEPTOR IN THE PLASMA-MEMBRANE - IMPLICATIONS FORTHE ACTIONS OF ENVIRONMENTAL ESTROGENS

Environmental or nutritional estrogenic toxicants are thought to media te developmental and carcinogenic pathologies. Estrogen receptor (ER) measurements are currently used to predict hormonal responsiveness; th erefore all ER subpopulations should be considered. We have been invol ved in the immunoidentification and characterization of membrane stero id receptors in several systems and have recently shown that binding o f estradiol (E(2)) to a subpopulation of ERs (mER) residing in the pla sma membrane of GH(3) pituitary tumor cells mediates the rapid release of prolactin (PRL). Here we review these findings and present other i mportant characterizations of these receptors such as trypsin and seru m susceptibility, movement in the membrane, confocal localization to t he membrane, binding to and function of impeded ligands, and immunosep aration of cells bearing mER. We plan to use this system as a model fo r both the physiological and pathological nongenomic effects of estrog ens and estrogenic xenobiotics. Specifically, it should be useful as a n in vitro assay system for the ability of estrogenic xenobiotics to c ause rapid PRL release as an example of nongenomic estrogen effects.