RAPID SCREENING OF ENVIRONMENTAL CHEMICALS FOR ESTROGEN-RECEPTOR BINDING-CAPACITY

Over the last few years, an increased awareness of endocrine disruptin g chemicals (EDCs) and their potential to affect wildlife and humans h as produced a demand for practical screening methods to identify endoc rine activity in a wide range of environmental and industrial chemical s. While it is clear that in vivo methods will be required to identify adverse effects produced by these chemicals, in vitro assays can defi ne particular mechanisms of action and have the potential to be employ ed as rapid and low-cost screens for use in large scale EDC screening programs. Traditional estrogen receptor (ER) binding assays are useful for characterizing a chemical's potential to be an estrogen-acting ED C, but they involve displacement of a radioactive ligand from crude re ceptor preparations at low temperatures. The usefulness of these assay s for realistically determining the ER binding interactions of weakly estrogenic environmental and industrial compounds that have low aqueou s solubility is unclear. In this report, we present a novel fluorescen ce polarization (FP) method that measures the capacity of a competitor chemical to displace a high affinity fluorescent ligand from purified , recombinant human ER-alpha at room temperature. The ER-alpha binding interactions generated for 15 natural and synthetic compounds were fo und to be similar to those determined with traditional receptor bindin g assays. We also discuss the potential to employ this FP technology t o binding studies involving ER-beta and other receptors. Thus, the ass ay introduced in this study is a nonradioactive receptor binding metho d that shows promise as a high throughput screening method for large-s cale testing of environmental and industrial chemicals for ER binding interactions.