Distribution of selected essential (Co, Cu, Fe, Mn, Mo, Se, and Zn) and nonessential (Cd, Pb) trace elements among protein fractions from hepatic cytosol of European chub (Squalius cephalus L.)

Abstract

Association of selected essential (Co, Cu, Fe, Mn, Mo, Se, and Zn) and nonessential (Cd, Pb) trace elements with cytosolic proteins of different molecular masses was described for the liver of European chub (Squalius cephalus) from weakly contaminated Sutla River in Croatia. The principal aim was to establish basic trace element distributions among protein fractions characteristic for the fish living in the conditions of low metal exposure in the water. The fractionation of chub hepatic cytosols was carried out by size exclusion high performance liquid chromatography (SE-HPLC; Superdex™ 200 10/300 GL column), and measurements were performed by high resolution inductively coupled plasma mass spectrometry (HR ICP-MS). Elution profiles of essential elements were mostly characterized by broad peaks covering wide range of molecular masses, as a sign of incorporation of essential elements in various proteins within hepatic cytosol. Exceptions were Cu and Fe, with elution profiles characterized by sharp, narrow peaks indicating their probable association with specific proteins, metallothionein (MT), and ferritin, respectively. The main feature of the elution profile of nonessential metal Cd was also single sharp, narrow peak, coinciding with MT elution time, and indicating almost complete Cd detoxification by MT under the conditions of weak metal exposure in the water (dissolved Cd concentration ≤0.3 μg L(-1)). Contrary, nonessential metal Pb was observed to bind to wide spectrum of proteins, mostly of medium molecular masses (30-100 kDa), after exposure to dissolved Pb concentration of ~1 μg L(-1). The obtained information within this study presents the starting point for identification and characterization of specific metal/metalloid-binding proteins in chub hepatic cytosol, which could be further used as markers of metal/metalloid exposure or effect on fish.

Cytosolic Distribution of Metals (Cd, Cu) and Metalloids (As, Se) in Livers and Gonads of Field-Collected Fish Exposed to an Environmental Contamination Gradient: An SEC-ICP-MS Analysis

“…In 1991, Klaverkamp et al [12] reported that in white suckers collected from a metal-contaminated environment, half of the hepatic Cu burden was bound to MT. Our results showed that Cu distribution in white suckers agreed with previous studies investigating Cu-binding biomolecules in the liver of freshwater fish collected in metal-impacted areas, where most of Cu was present at the same elution time as the elution time for MT (European eels (Anguilla anguilla) [13,14]; European chub and Vardar chub (Squalius cephalus and S. vardarensis) [15,16]; gibel carp (Carassius auratus gibelio) [17]). Comparable interpretations were made in field-collected juvenile yellow perch (Perca flavescens), although the major Cu peak did not elute at exactly the same elution time as was observed for the MT standard [18]; many isoforms of MTs co-exist and may explain this difference [17].…”

“…Co-elution with Cu was also reported, and the authors speculated that the metal-binding ligand was probably MT. Cadmium presence in the cytosol and its probable binding to MT were previously reported for the liver and gills of Vardar and European chubs collected in metal mining-impacted rivers [15,16,19]. Increased Cd associated with hepatic MT was also reported in field-collected European eels (Anguilla anguilla) and gibel carp (Carassius auratus gibelio) [14,17].…”

Accumulation of metals relevant for agricultural contamination in gills of European chub (Squalius cephalus)

“…Our results are in accordance with the demonstration made by Bury and Grosell (2003) that Fe can be absorbed from the water by the gills in teleost fish. In addition, among essential elements, Fe is well known for its tendency to accumulate in living organisms in a form of ferritin, especially in fish liver (Krasnići et al 2013). Unlike Fe, which was observed to accumulate in different chub organs , the most of the essential elements are kept within narrow boundaries in fish organism, and only the conditions of high metal exposure, much higher compared to naturally found water metal concentrations, would result in metal bioaccumulation in fish organs.…”

Cytosolic distributions of highly toxic metals Cd and Tl and several essential elements in the liver of brown trout (Salmo trutta L.) analyzed by size exclusion chromatography and inductively coupled plasma mass spectrometry

“…Caron et al (2018) applied similar methodology to perform somewhat more extensive study on liver of juvenile yellow perch (Perca flavescens) regarding binding of several trace elements (Ag, Cd, Co, Cu, Ni, and Tl) to various cytosolic biomolecules. Our previous studies in this field included comprehensive investigation of cytosolic distributions of Cd, Co, Cu, Fe, Mn, Mo, Pb, Se, and Zn in the liver and gills of European chub (Squalius cephalus) from the moderately contaminated Sutla River in Croatia (Krasnići et al, 2013(Krasnići et al, , 2014 and of Vardar chub (Squalius vardarensis) from highly contaminated Macedonian rivers .…”

“…/j.chemosphere.2018 5 and to define the distribution profiles among cytosolic biomolecules of different molecular masses for nine selected elements, two highly toxic metals (Cd and Tl) and seven essential elements (Co, Cu, Fe, Mn, Mo, Se, and Zn). As it is very likely that various fish species have different metal handling strategies, the additional aim of this study was to compare metal distribution profiles characteristic for brown trout liver with previously published profiles for liver of European chub (Krasnići et al, 2013) and…”