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.

Physiological effects of temperature and a herbicide mixture on the soft-shell clam Mya arenaria (Mollusca, Bivalvia).

The aim of the current study was to investigate effects of temperature and a mixture of herbicides on the physiological status of the bivalve Mya arenaria. Bivalves acclimated to two temperatures (7 and 18°C) were exposed for 28 d to 0.01 mg/L of a pesticide formulation containing dichlorophenoxyacetic acid (2,4-D), 2-(2-methyl-4-chlorophenoxy) propionic acid (mecoprop), and 3,6-dichloro-2-methoxybenzoic acid (dicamba). At days 7, 14, and 28, mortality, immune parameters (hemocyte number, phagocytic activity, and efficiency), biomarkers of oxidative stress (catalase [CAT] and superoxide dismutase [SOD] activities and malondialdehyde [MDA] content), the metabolic enzyme cytochrome C oxidase (CCO), a biomarker of pesticide exposure (acetylcholinesterase [AChE]), and the activity of an enzyme related to gametogenesis (aspartate transcarbamylase [ATCase]) were monitored in clam tissues. Gonadosomatic index (GSI), condition factor (CF), and sex were also assessed. In clams acclimated to 7°C, exposure to pesticide enhanced CCO activity and CF and decreased MDA content, hemocyte number, CAT, and SOD activities. In clams kept at 18°C, pesticide effects appeared minor compared with samples kept at 7°C. In bivalves acclimated to 18°C, CCO, SOD, and ATCase activity and MDA content were enhanced, and hemocyte number, CAT, and AchE activities and phagocytosis were suppressed. In samples exposed to pesticides, increased temperature enhanced MDA content and CCO and SOD activity and suppressed hemocyte number and CAT and AchE activity. A gradual sexual maturation was observed in both sexes through experimental time, but females had a higher sensitivity to temperature and pesticides compared to males. Increased temperature altered the ability of the sentinel species Mya arenaria to respond to pesticide exposures. Further work is needed to understand the impacts of increasing temperature on the whole St. Lawrence estuary ecosystem.