Distribution of antidepressants and their metabolites in brook trout exposed to municipal wastewaters before and after ozone treatment – Evidence of biological effects

This study examined the tissues distribution of selected serotonin reuptake inhibitors (SSRIs) in brook trout exposed for 3 months to continuous flow-through primary-treated effluent before and after ozone treatment. A reliable analytical method was developed for the quantification of trace amounts of antidepressants in small tissue homogenate extracts. Levels of six antidepressants and four of their N-desmethyl metabolites were determined using liquid chromatography–tandem mass spectrometry. Significant amounts of the SSRIs were found in fish tissue—in decreasing order: liver > brain > muscle. Sertraline and its metabolite desmethylsertraline were the predominant substances observed in most tissues (0.04–10.3 ng g−1). However, less SSRIs (0.08–1.17 ng g−1) were bioaccumulated in the ozonated effluent. The early molecular effects of these SSRIs on the Na/K-dependent ATPase pump activity in brain synaptosomes where also investigated in vitro and in fish exposed to the municipal effluents. With respect to their potential biological effects, in vitro exposure to selected SSRIs induced a reduction of the brain Na/K-ATPase activity in synaptosomes in a dose-dependent manner. Results showed that Na/K-ATPase activity was readily inhibited by exposure to municipal effluent before and, to a lesser extent, after ozone treatment. Moreover, the Na/K-ATPase activity was significantly and negatively correlated with brain tissue concentrations of fluoxetine (r = −0.57; p < 0.03), desmethylsertraline (r = −0.84; p < 0.001), and sertraline (r = −0.82; p < 0.001). The present study reveals that SSRIs are readily available in fish, biologically active and corroborates previous findings on the serotonergic properties of municipal effluents to aquatic organisms.

Research highlights
► We have developed a reliable analytical method for the quantification by LC–MS/MS of trace amounts of antidepressants in small fish tissues homogenate extracts.
► Following exposure to municipal wastewater, we found significant amounts of antidepressants bioaccumulated in brook trout tissue—in decreasing order: liver > brain > muscle.
► We have proposed the Na/K-ATPase pump activity as biomarker of exposure to antidepressants.
► We observed a significant correlated relationship between the biomarker response in brain synaptosomes and the brain tissue concentrations of certain antidepressants.