Aromatase inhibition is one of the chemical modes of action of concern to EPA's Endocrine Disruptor Screening Program (EDSP). In vitro bioassays that can detect aromatase inhibition are part of both the EDSP tier 1 screening program and are included subset of ToxCast assays employed for EDSP21 screening. An adverse outcome pathway (AOP) linking aromatase inhibition to reproductive dysfunction in fish has been described and endorsed by the OECD, establishing a scientifically sound connection between aromatase inhibition and adverse apical outcomes relevant to risk assessment and regulatory decision-making. Further, computational models that allow for quantitative prediction of dose-response time-course behaviors and the potential severity of the adverse outcome based on in vitro screening data have been developed. The present study provides further weight of evidence to support this AOP and its use in regulatory decision-making. In particular, it identifies rapid responses to aromatase inhibition that can be expected to occur within the first 24 h of exposure, examines the dynamic stability of gene expression responses over that period to help identify appropriate time periods in which characteristic gene expression responses may serve as effective biomarkers of exposure to aromatase inhibitors, and provides insights into different gene regulatory mechanisms that may be operating over the first few hours of exposure versus more systemic endocrine-related regulation that appear to take over after 6-12 h of exposure. These data continue to refine our understanding of this important mode of endocrine disruption and how to more efficiently and effectively both model and test for it to support regulatory decision-making.

This dataset is associated with the following publication: Schroeder, A., G. Ankley, T. Habib, N. Garcia-Reyero, B. Escalon, K. Jensen, M. Kahl, E. Durhan, E. Makynen, J. Cavallin, D. Martinovic-Weigelt, E. Perkins, and D. Villeneuve. Rapid effects of the aromatase inhibitor fadrozole on steroid production and gene expression in the ovary of female fathead minnows (Pimephales promelas). GENERAL AND COMPARATIVE ENDOCRINOLOGY. Academic Press Incorporated, Orlando, FL, USA, 252: 79-87, (2017).