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Correlation between MXR inhibitors in wastewater and zebrafish embryotoxicity

Waste water treatment plants (WWTPs) are important point sources of a broad range of xenobiotics in the aquatic environment. Once released from WWTPs, xenobiotics represent a potential risk to environment, but also to human health. Since it is very hard to predict their possible impact on different levels of biological organization, it is necessary to use "early warning" biomarkers that can provide informations on potential environmental impact. Zebrafish embryos are frequently used organisms in ecotoxicology studies due to their short embryonic ontogenesis and transparent chorion. The fish embryo test (FET), as a substitute for acute toxicity with adult zebrafish, is a great biomarker in toxicity testing of pollutants that are residues from incomplete elimination in WWTPs. Screening sub-lethal and lethal endpoints after exposure to wastewater included coagulation of embryos, presence of somites, tail detachment, heart functioning, blood circulation, pigmentation, formation of edema and developmental retardation. Zebrafish embryos also possess multixenobiotic resistance mechanism (MXR) mediated by ABC transport proteins that acts as a protective barrier against the cell uptake and accumulation of potentially toxic compounds dissolved in the water. MXR mechanism can be modified by the presence of a wide range of xenobiotics frequently present in wastewaters (pharmaceuticals, chemicals used in industry and agriculture, personal care producs). Concentration of model fluorescent substrate in the embryo after exposure to environmental samples, give us an insight into the degree of inhibition and accumulation of xenobiotics from wastewater in the whole embryo. The integration of embryotoxicity and MXR creates a sensitive tool for the evaluation of early developmental responses of zebrafish to xenobiotics present in wastewaters on whole organism level, but also on the cellular level. These responses help us to understand better possible toxic effects of wastewater effluents on aquatic organisms.

Danio rerio ; zebrafish ; MXR ; embryotoxicity

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