engleski

Electrochemically determined metallothioneins as indicators of wastewater-borne metal exposure in the Krka River

Among various pollutants in the aquatic ecosystems, metals pose a serious threat due to their toxicity and potential for bioaccumulation. To assess the overall impact of metal exposure in aquatic environments, bioindicator organisms are commonly used. An early warning biological sign of metal exposure is the induction of metallothioneins (MTs), cytosolic proteins responsible for metal homeostasis and detoxification [1]. In this study, MT levels were used to evaluate metal exposure in fish intestinal parasite Dentitruncus truttae Sinzar, 1955 and its host brown trout (Salmo trutta Linnaeus, 1758) from the karst Krka River. Although the lower part of the Krka River course was proclaimed a national park, its upper course is impacted by inadequately treated wastewaters, which are the main anthropogenic source of metals in the river. MT concentrations were compared among fish liver, as a site of metal detoxification, fish intestine, as a site of metal uptake, and D. truttae, which absorb nutrients from the intestinal tract of fish but also efficiently accumulate metals. Fish were caught at the Krka River source (KRS), the reference site, downstream of the wastewater outlets (KRK) and at hydropower plant Miljacka, situated in the national park (KNP). MTs were quantified by differential pulse voltammetry (DPV) using modified Brdička procedure, a commonly used electrochemical method for the determination of proteins containing thiol groups. DPV was confirmed as a reliable and sensitive method for measuring MTs in biological samples. MT concentrations were significantly higher in D. truttae than in fish gut and liver, and represent the first data for these parasites [2]. D. truttae also showed differences among locations, with the highest MT levels in KRK (2, 2 mg g-1 wet tissue), indicating metal-induced stress near the wastewater outlets.

differential pulse voltammetry ; Dentitruncus truttae ; biomarkers

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