Screening of dioxin-like toxicity equivalents for various matrices with wildtype and recombinant rat hepatoma H4IIE cells

Determination of dioxin-like compounds utilizing in vitro bioassays such as ethoxyresorufin-O-deethylase (EROD) or chemical-activated luciferase expression (DR-CALUX®) is an important tool to evaluate their Ah receptor-mediated toxic effects. The aim of this study is to describe advantages and limitations of these bioassays using rat hepatoma (H4IIE) wildtype and recombinant H4IIE cells in a 96 well microtiter plate format. We are using these bioassays for the evaluation of relative responses (REP) from several congeners of dioxins (e.g., 2,3,4,7,8-PCDF) or dioxin-like compounds (PCB-126, 2,3,4,7,8-PBDF) to 2,3,7,8-TCDD. In addition, total toxic equivalency factors (TEFs) of mixtures of these dioxin-like compounds from several kinds of matrices such as feed, sediment, or thermal waste residues are measured by both bioassays and additional chemical analysis. These samples were measured in a cross-validation study between two laboratories using the DR-CALUX technology in comparison to the H4IIE-EROD assay and chemical analysis. Improvement of the quality criteria of the newly developed DR-CALUX bioassays in comparison to the EROD bioassay was demonstrated (higher coefficient of determination r