engleski

Changes in cytosolic distribution of toxic metals Cd and Pb in liver, gills and intestine of Vardar chub (Squalius vardarensis)induced by exposure to mining effluents

Mining effluents significantly contribute to metal contamination of freshwaters, presenting an important environmental concern. Aquatic organisms exposed to increased metal levels have various detoxification strategies, such as binding of accumulated metals to specific cytosolic ligands. However, a part of metal accumulated within the cell can still bind to important biological molecules and cause toxic effects. The aim of our study was to establish the changes in Cd and Pb distribution among cytosolic proteins in three organs (gills, liver, intestine) of Vardar chub (Squalius vardarensis), which could have occurred due to increased exposure to Cd and Pb in two mining impacted rivers in north-eastern Macedonia (Zletovska and Kriva) in comparison to the reference Bregalnica River. Size-exclusion high performance liquid chromatography was applied for cytosolic protein separation according to their molecular masses whereas high resolution inductively coupled plasma mass spectrometry was used for metal measurement in obtained fractions, as well as in total cytosolic fractions of three chub organs. In all three organs, the majority of Cd was eluted with low molecular mass proteins (LMM ; 10-30 kDa) with maximum at elution time of metallothioneins (MT ; 12.5 kDa). Increase of Cd bioaccumulation resulted mainly with the increase of that MT-peak height, which was most pronounced in chub from mining impacted rivers and corresponded well to cytosolic Cd concentrations. Occurrence of additional peak due to increase in Cd bioaccumulation was observed only in the gill cytosol, where small Cd portion was found associated with high molecular mass proteins (HMM ; >100 kDa). The best resolved and the highest Pb peaks were found in the chub from the Kriva River, characterized by the highest Pb exposure in the water and the highest Pb bioaccumulation. Unlike Cd, distribution profiles of Pb notably differed between three organs. In liver, two sharp peaks were observed within HMM and LMM regions, where LMM peak coincided with elution time of MTs. In gills, several peaks in HMM and medium molecular mass (MMM ; 30-100 kDa) regions were found, but were rather small and not well resolved. In the intestine, Pb was mainly eluted in MMM protein region in clear, sharp peak with maximum at 35.9 kDa. The changes of distribution profiles of Cd and Pb in three organs of Vardar chub clearly reflected the exposure and bioaccumulation levels of these metals.

heavy metals ; HPLC ; Vardar chub ; liver ; gills ; intestine ; cytosolic distribution

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