Tissue-specific uptake of the benzodiazepine oxazepam in adult Eurasian perch (Perca fluviatilis)

Abstract

Environmental contextAlthough pharmaceuticals are found in wild fish, there is no consensus as to which fish tissue to use when measuring the pharmaceutical concentrations. Using the psychiatric pharmaceutical oxazepam in Eurasian perch as an example, we found that oxazepam was distributed in the perch tissues in the following order of concentration: muscle<liver=brain<blood plasma. These results help to interpret and compare previous studies, and provide guidance for future studies. AbstractPsychoactive substances are used worldwide and constitute one of the common groups of pharmaceutical contaminants in surface waters. Typically, in field surveys and laboratory studies, muscle or whole-body homogenates are used to quantify pharmaceutical concentrations in biota, although uptake of pharmaceuticals may be tissue-specific. Therefore, the aim of this study was to investigate the tissue-specific (muscle, liver, brain and blood plasma) uptake of the anxiolytic oxazepam in adult Eurasian perch (Perca fluviatilis). In laboratory experiments, perch were exposed to four different concentrations (2, 4, 12 and 20µgL–1) of oxazepam for 6 days, and muscle, liver, brain tissue and blood plasma were sampled to determine tissue-specific bioconcentration. We found that the tissue-specific bioconcentration was independent of oxazepam concentration. However, among tissue types, bioconcentration was significantly different, with the concentration in muscle<liver=brain<blood plasma. Hence, it is important to consider the type of tissue used to quantify pharmaceutical uptake in fish, for predictions of species-specific sensitivity and comparisons across studies. Furthermore, our results indicate a somewhat lower transportability (brain/plasma ratio 0.54) of oxazepam from blood to brain in fish compared with in mammals, which should be kept in mind when employing ‘read-across’ approaches.