Chemical screening in an estrogen receptor transactivation assay with metabolic competence

The U.S. EPA continues to utilize high-throughput screening data to evaluate potential biological effects of endocrine active substances without the use of animal testing. Determining the scope and need for in vitro metabolism in high-throughput assays requires the generation of larger data sets that assess the impact of xenobiotic transformations on toxicity-related endpoints. The objective of the current study was to screen a set of 768 ToxCast chemicals in the VM7Luc estrogen receptor transactivation assay (ERTA) using the Alginate Immobilization of Metabolic Enzymes (AIME) hepatic metabolism method. Chemicals were screened with or without metabolism to identify estrogenic effects and metabolism-dependent changes in bioactivity. Based on estrogenic hit calls, 85 chemicals were active in both assay modes, 16 chemicals were only active without metabolism, and 27 chemicals were only active with metabolism. Using a novel metabolism curve shift method that evaluates the shift in concentra...