A physiologically based toxicokinetic (PBTK) model describing the bioaccumulation of two perfluorinated substances in rainbow trout (Onchorynchus mykiss)
Résumé
Per- and poly-fluorinated substances (PFASs) are ubiquitous in the environment, specifically in aquatic systems. While several PFASs are acknowledged to be bioaccumulated by vertebrate species, including fish, their absorption, distribution, metabolisation and elimination (ADME) remain incompletely understood yet. The aim of this study is to develop a physiologically based toxicokinetic (PBTK) model in order to describe the mechanisms in rainbow trout (Oncorhynchus mykiss) exposed through the diet to two selected PFASs, namely perfluorooctane sulfonic acid - PFOS - and perfluorohexane sulfonic acid – PFHxS. Here PFOS is considered as a model compound, as it remains the dominant PFAS in environmental matrices. PFHxS represents an industrial alternative to PFOS, since its addition to Annex B of the Stockholm convention in 2009. Dietary exposure experiments were performed on adult rainbow trouts at two water temperatures (7°C and 11°C). 200 fish were fed daily using pellets spiked with a mixture of PFOS and PFHxS during several weeks. Then, fish were allowed to depurate, in the same tanks, where non contaminated food was supplied daily. During both phases, 5 randomly selected fish were periodically sacrificed. Organs and blood were sampled, weighted, and prepared for PFOS and PFHxS analysis (UPLC-MS/MS). Data from these two dietary experiments, as well as this obtained from the literature, were used for the model calibration. The present PBTK model comprises seven compartments: arterial and venous blood, liver, viscera, brain, kidney, and muscle. Uptake is considered to occur exclusively by diet and no biotransformation of the selected PFASs is considered, since PFOS and PFHxS are final products of precursor degradation. Also, the model took into account growth of individuals and temperature variation, both variables which may influence ADME processes in fish.