METALTRANSP · Characterization of the trace metals transport and interaction mechanisms in zebrafish Danio rerio using molecular and stable isotope approaches

Due to anthropogenic activities, concentrations of both essential and non-essential elements in surface waters are often far above the natural levels imposing a threat to the health of aquatic organisms. At present, Biotic Ligand Model (BLM) is the most widely used computational concept used for setting water quality criteria. It predicts the effects of water chemistry on metal bioavailability and toxicity by linking metal speciation in solution with the amount of accumulated metal and relating that to the toxicity. However, the links between metal accumulation and toxicity are complex. Therefore, to create a model which would effectively correlate laboratory-based predictions and field observations, bioaccumulation processes must be understood and quantified. This requires consideration of not only the total metal accumulated in tissues, but also determination of internal metal reactions, and quantification of uptake, detoxification (metal partitioning) and elimination processes in the organisms. The objectives of the current proposal are to identify the metal transporting proteins in zebrafish Danio rerio that are responsible for essential (Cu, Fe, Zn) and non-essential (Cd and Pb) trace metal transport during multimetal exposure and to assess the influence of multimetal interactions on compartmentalization of individual metals in tissues. To address these tasks, gene expression patterns will be correlated to metal uptake in vivo. Then, the identified candidate transporters will be over expressed in a Xenopus oocyte expression system and metal uptake affinities (Cu, Fe, Zn, Cd and Pb) will be determined. Metal uptake and elimination studies, as well as investigation of the effects from multimetal exposure on distribution of individual metals in the body, will be performed using a novel stable isotope approach, which enables accurate determination of amounts of metal accumulated at low, environmentally relevant exposure concentrations.