Different uranium distribution patterns in cytosolic protein pool of zebrafish gills after chronic and acute waterborne exposures Guillaume Bucher a,b , Sandra Mounicou b , Olivier Simon a , Magali Floriani a , Ryszard Lobinski b , Sandrine Frelon a,⇑ a IRSN/PRP-ENV/SERIS, Laboratoire de Biogéochimie, Biodisponibilité et Transferts des radionucléides, BP3, 13115 St Paul lez Durance Cedex, France b LCABIE, UMR5254, Technopôle Hélioparc Pau Pyrénées, 2 avenue du Président Angot, 64053 Pau Cedex 09, France highlights  Screening of U distribution among proteins in gill cytosols of U exposed zebrafish.  Significant U bioaccumulation in gills after 3 d of realistic chronic exposure.  Different U-protein distribution patterns in cytosols as function of exposure level.  Higher amount of U in the cytosolic fraction in case of high exposure level.  Potential effect of U on Zn cytosolic burden. article info Article history: Received 17 July 2013 Received in revised form 17 March 2014 Accepted 22 March 2014 Handling Editor: Klaus Kümmerer Keywords: Zebrafish Gills Uranium speciation SEC–ICP-SFMS Cytosolic distribution abstract The toxicity of uranium (U) to aquatic organisms depends notably on its compartmentalization in organs, tissues, cells as well as on its distribution among biomolecules. In order to contribute to the understand- ing of U accumulation and associated toxicity mechanisms in case of waterborne exposure, this study focused on U fate in the gills epithelia, uptake pathway, of the fish model Danio rerio (zebrafish). U dis- tribution among cytosolic biomolecules was investigated after no addition (0 lgL 1 (c 0 ) for 3 and 30 d), chronic (20 lgL 1 (c 20 ) for 30 d) and acute (20 lgL 1 (c 20 ) and 250 lgL 1 (c 250 ) for 3 d) exposures to depleted U. Cytosolic U accounted for an average of 24–32% of gills burden for c 20 and c 250 , respectively. Size Exclusion Chromatography (SEC) coupled with Inductively Coupled Plasma-Sector Field Mass Spec- trometry (ICP-SFMS) allowed identification of ecotoxicologically relevant U-containing fractions among cytosolic biomolecules as a function of exposure conditions. In c 0 and c 20 samples, most U (ca. 80%) was found in the Low Molecular Weight fraction (LMW, <18 kDa), often considered as a detoxifying frac- tion. In c 250 exposed fish, U was equally distributed between LMW (40%) and High Molecular Weight (HMW, 150–670 kDa; 40%) fractions, the latter including sensitive metalloproteins. Uranium-biomole- cules were co-eluted with endogenous essential metal (Fe, Cu and Zn) species, however, no major influ- ence on their cytosolic concentration and distribution pattern among cytosolic proteins was found. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Various approaches have been developed to assess metal toxic- ity in aquatic living organisms over many years (Campbell et al., 2004). The Critical Body Residue (CBR), which proposes to link the toxicity of a metal to its bioaccumulation within organisms, suggests that organisms are able to distribute the metal burden among metabolically available (e.g. cytosol, organelles) and detox- ified (e.g. metal-rich granules) cell compartments (Vijver et al., 2004; Adams et al., 2011). Thus, the determination of metal com- partmentalization at the organ and subcellular levels is necessary (i) to better understand the kinetics of metal distribution into a biological cell or tissue and (ii) to better define the relationship between metal bioaccumulation and its biological effect. Within this compartmentalization, the cytosol of cells is of significant importance in the identification of toxic metal fractions as this compartment is known to have an important role in the toxicoki- netics and toxicodynamics of metals (Amiard et al., 2006; Perceval et al., 2006; Geffard et al., 2010). It contains several pro- teins dedicated to detoxification, the latter occurring mainly via an association between proteins or other organic molecules and http://dx.doi.org/10.1016/j.chemosphere.2014.03.110 0045-6535/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +33 (0)442 19 94 71. E-mail address: sandrine.frelon@irsn.fr (S. Frelon). Chemosphere 111 (2014) 412–417 Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere