title: Key learnings from performance of the U.S. EPA Endocrine Disruptor Screening Program (EDSP) Tier 1 in vitro assays.
abstract: Tier 1 of the U.S. EPA Endocrine Disruptor Screening Program comprises 11 studies: five in vitro assays, four in vivo mammalian assays, and two in vivo nonmammalian assays. The battery is designed to detect compounds with the potential to interact with the estrogen, androgen, or thyroid signaling pathways. This article examines the procedures, results, and data interpretation for the five Tier 1 in vitro assays: estrogen receptor (ER) and androgen receptor binding assays, an ER transactivation assay, an aromatase assay, and a steroidogenesis assay. Data are presented from two laboratories that have evaluated approximately 11 compounds in the Tier 1 in vitro assays. Generally, the ER and androgen receptor binding assays and the aromatase assay showed good specificity and reproducibility. As described in the guideline for the ER transactivation assay, a result is considered positive when the test compound induces a reporter gene signal that reaches 10% of the response seen with 1 nM 17β-estradiol (positive control). In the experience of these laboratories, this cutoff criterion may result in false-positive responses. For the steroidogenesis assay, there is variability in the basal and stimulated production of testosterone and estradiol by the H295R cells. This variability in responsiveness, coupled with potential cell stress at high concentrations of test compound, may make it difficult to discern whether hormone alterations are specific steroidogenesis alterations (i.e., endocrine active). Lastly, both laboratories had difficulty meeting some recommended performance criteria for each Tier 1 in vitro assay. Data with only minor deviations were deemed valid.
authors: Toxicology & Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan.
authors: Matthew J
authors: MJ
authors: LeBaron
authors: Katie K
authors: KK
authors: Coady
authors: John C
authors: JC
authors: O'Connor
authors: Diane L
authors: DL
authors: Nabb
authors: Lauren K
authors: LK
authors: Markell
authors: Suzanne
authors: S
authors: Snajdr
authors: M
authors: M
authors: Sue Marty
mesh_terms: D000818:Animals; D001141:Aromatase / Q000378:metabolism; D001681:Biological Assay / Q000379:methods*; D052244:Endocrine Disruptors / Q000032:analysis* / Q000633:toxicity*; D006801:Humans; D011944:Receptors, Androgen / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism; D013256:Steroids / Q000096:biosynthesis; D018675:Toxicity Tests / Q000379:methods*; D014481:United States; D014484:United States Environmental Protection Agency
chemical_list: D052244:Endocrine Disruptors; D011944:Receptors, Androgen; D011960:Receptors, Estrogen; D013256:Steroids; D001141:Aromatase
keywords: EDSP; Tier 1; androgen receptor binding; aromatase; endocrine disruptor screening program; estrogen receptor binding; estrogen receptor transactivation; in vitro; steroidogenesis