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Evaluating Several in vitro Disposition Models for use in High-throughput Toxicokinetic Research
Citation:
Lasee, S., J. Nyffeler, B. Blackwell, J. Harrill, F. Harris, J. Haselman, J. Nichols, AND Dan Villeneuve. Evaluating Several in vitro Disposition Models for use in High-throughput Toxicokinetic Research. Society of Environmental Toxicology and Chemistry (SETAC) North America, Pittsburgh, PA, November 13 - 17, 2022. https://doi.org/10.23645/epacomptox.21561270
Impact/Purpose:
In vitro high-throughput screening assays are increasingly being used to generate toxicity data. To compare this screening data with standardized testing, it is critical to understand the bioavailable fraction of dosed chemical in high-throughput assays. In the current study, multiple in vitro disposition models are used to generate estimated of free chemical in a rainbow trout gill cell assay. Final outputs will be compared across models and eventually with measured chemical concentrations to determine which model(s) best describe chemical behavior within this in vitro system to more accurately calculate the in vitro dose.
Description:
In vitro high-throughput screening assays are being increasingly adopted as part of a tiered testing strategy for chemical hazard evaluation. As such, it has become important to understand chemical behavior within in vitro assay systems to accurately predict the bioavailable chemical concentration at a calculated nominal in vitro potency. Several in vitro distribution models have been developed to predict chemical partitioning using physiochemical properties along with assay specific parameters including well dimensions, cell density, and serum protein content. The purpose of this study was to use available models to predict chemical distribution in a 384-well format version of OECD test guideline 249 (OECD TG249) for cell viability testing in rainbow trout gill cells (RTgill-W1). A total of 231 environmentally relevant chemicals were chosen for screening in the assay based on available in vivo rainbow trout toxicity, in vitro toxicity, or known environmental occurrence. Final model outputs will be applied to the nominal point-of-departure (POD) to calculate a free chemical concentration, which will then be used for in vitro-to-in vivo extrapolation. Currently, assay specific model input parameters have been determined, and in vitro distribution estimates were generated for 201 of our 231 test chemicals using the Armitage 2014 model. The remaining 30 chemicals, which included polymers, ionic compounds, and metals, were excluded due to model incompatibility. The log Kow for input chemicals ranged -2.63 to 7.61, and the fraction of freely dissolved chemical in cell media (Ffree) ranged 0.0002 to 1.0. The Armitage 2014 model is largely Kow dependent and predicted Ffree in this assay drops below 0.5 at a log Kow of approximately 3.9. Future outputs from the Fischer 2017, Fisher 2019, Armitage 2014, and Armitage 2021 models will be compared to identify chemical domains showing agreement (or lack thereof) across the different modeling approaches. Ultimately, the modeled chemical distribution will be compared with empirically measured concentrations of a subset of 12 chemicals to assess model performance and determine which model(s) best describe chemical behavior within this in vitro system to more accurately calculate PODs using in vitro-to-in vivo extrapolation. The contents of this abstract neither constitute, nor necessarily reflect, official US EPA policy.
URLs/Downloads:
DOI: Evaluating Several in vitro Disposition Models for use in High-throughput Toxicokinetic Research
STEVEN LASEE - SETAC 2022 PRESENTATION_FINAL.PDF (PDF, NA pp, 527.671 KB, about PDF)