Measured and Modeled Toxicokinetics in Cultured Fish Cells and Application to In Vitro - In Vivo Toxicity Extrapolation

Abstract

Effect concentrations in the toxicity assessment of chemicals with fish and fish cells are generally based on external exposure concentrations. External concentrations as dose metrics, may, however, hamper interpretation and extrapolation of toxicological effects because it is the internal concentration that gives rise to the biological effective dose. Thus, we need to understand the relationship between the external and internal concentrations of chemicals. The objectives of this study were to: (i) elucidate the time-course of the concentration of chemicals with a wide range of physicochemical properties in the compartments of an in vitro test system, (ii) derive a predictive model for toxicokinetics in the in vitro test system, (iii) test the hypothesis that internal effect concentrations in fish (in vivo) and fish cell lines (in vitro) correlate, and (iv) develop a quantitative in vitro to in vivo toxicity extrapolation method for fish acute toxicity. To achieve these goals, time-dependent amounts of organic chemicals were measured in medium, cells (RTgill-W1) and the plastic of exposure wells. Then, the relation between uptake, elimination rate constants, and log KOW was investigated for cells in order to develop a toxicokinetic model. This model was used to predict internal effect concentrations in cells, which were compared with internal effect concentrations in fish gills predicted by a Physiologically Based Toxicokinetic model. Our model could predict concentrations of non-volatile organic chemicals with log KOW between 0.5 and 7 in cells. The correlation of the log ratio of internal effect concentrations in fish gills and the fish gill cell line with the log KOW was significant (r>0.85, p = 0.0008, F-test). This ratio can be predicted from the log KOW of the chemical (77% of variance explained), comprising a promising model to predict lethal effects on fish based on in vitro data.

Assessing the impact of benzo[ a ]pyrene with the in vitro fish gut model: An integrated approach for eco-genotoxicological studies

“…For many years, assays using cell lines derived from fish have been proposed as alternatives to animal use in aquatic toxicity testing with excellent reviews on the topic available [6][7][8][9][10][11]. More recently, they have been proposed as in vitro-in vivo toxicity extrapolation tools [12][13][14][15], in addition to adding information complimentary to adverse outcome pathway (AOP) predictions [16].…”

“…xenobiotic-metabolising organs, such as the liver and gill in rainbow trout (Oncorhynchus mykiss), a model fish species [11,13,14,[18][19][20][21][22], but are readily available from numerous fish species [23].…”

A physiologically based toxicokinetic (PBTK) model for moderately hydrophobic organic chemicals in the European eel ( Anguilla anguilla )

“…In order to realise the full potential of the proposed methodology, the European eel PBTK model can be extended by the inclusion of toxicodynamic (TD) models, resulting in a PBTK/TD model. PBTK models have been used successfully to link results of in vitro bioassays with in vivo effects (Brinkmann et al, 2014a;Stadnicka-Michalak et al, 2014). With the present model, toxicological data from European eels can thus be retrospectively linked to internal concentrations at the target site.…”

“…PBTK models are capable of predicting the concentration of neutral organic pollutants in the whole fish and in different tissues at any time during exposure (Louisse et al, 2012;Yoon et al, 2012). Furthermore, they facilitate application of the results of in vitro bioassays, which have a higher throughput and reduce the requirement for experimental animals, to predict the effects in vivo; these models thus have the potential to make a valuable contribution to predictive toxicology (Brinkmann et al, 2014a;Stadnicka-Michalak et al, 2014).…”

In Response: Adverse outcome pathways—An industry perspective

“…An integration of exposure (in real life often highly variable), toxicokinetic aspects (absorption, distribution, metabolism, and excretion), and thresholds for toxicity will be required. Progress is being made along these lines (e.g., Stadnicka‐Michalak et al ), but considerable work will be required to develop suitable models. These will require sufficient understanding of the most appropriate dose metrics and how they relate to variable exposures in the real world.…”