Bioconcentration, metabolism, and biomarker responses in freshwater fish Carassius auratus exposed to roxithromycin

To investigate the distribution, bioconcentration, metabolism, and biomarker responses of macrolide antibiotic roxithromycin (ROX) in fish, crucian carp (Carassius auratus) were exposed to various concentrations of ROX (4, 20, and 100 mu g L-1) for 20 d. The ROX content in different tissues was quantified using UPLC/MS/MS. The liver exhibited the highest ROX concentration followed by the bile, gills, and muscle tissues. After 15 d of exposure to different concentrations of ROX, the bioconcentration factors were 2.15-38.0 in the liver, 0.950-20.7 in the bile, 0.0506-19.7 in the gill, and 0.0439-13.8 in the muscle; these results were comparable to the estimated BCF values. The metabolites formed in the bile were identified based on metabolic identification in human bile. Additionally, the biomarkers, including acetylcholinesterase in the brain, as well as 7-ethoxyresorufin O-deethylase and superoxide dismutase in the liver changed significantly after 5, 10, 15, and 20 d of exposure (P < 0.05). Our results suggest that ROX can accumulate and be metabolized in fish; therefore, interactions between ROX or its metabolites and the biological systems may induce biochemical disturbances in fish. (C) 2013 Elsevier Ltd. All rights reserved.