engleski

Metal Exposure Assessment in Native Fish, Mullus barbatus, from the Eastern Adriatic Sea

Environmental contamination is steadily increasing due to diverse anthropogenic activities. In order to estimate the risk of metal exposure, reliable biomarkers as an early warning cellular mechanisms, have to be validated and applied in the field. Metal-associated stress in the organism is reflected in the induction of metallothioneins (MTs), cytosolic proteins responsible for essential metal homeostasis (Zn, Cu) and detoxification of toxic metals (Cd, Hg, Ag). Prerequisite for reliable application of MT, as a biomarker in native aquatic organisms, is to define differences between species and tissues, as well as physiological and environmental conditions that influence cellular MT and metal content. Age related MT and metal (Zn, Cu, Fe, Mn, Cd) variations have been studied in three indicator tissues of benthic fish Mullus barbatus from the Eastern Adriatic Sea. Liver and kidney are commonly used as indicator tissues, while intestine has been selected as primary uptake route for dietary metals. Liver cytosol is characterized by MT and essential metal association (Zn and Cu), reflecting the MT role in their homeostasis, while Cd accumulates with fish age (significant increase from 1 to 8 years old specimens ; b=2.84, R2=0.90). Cadmium accumulation also occurs in kidney tissue, but slower that in liver (b=1.03, R2=0.73). Intestinal MT level is associated with Cu level (R=0.38), without significant relation to age. MT levels are age-related in kidney, but not in liver and intestine. In native red mullet constitutive hepatic MT level amounts to 8.89 µ ; ; ; ; g mg^-1 proteins and intestinal to 28.3 µ ; ; ; ; g mg^-1 proteins. Metal distribution is tissue specific with highest cytosolic Cu and Cd levels in liver, Zn and Mn in intestine and Fe in kidney. Besides comparison of metal levels in different fish tissues related to age, comparison was performed for specimens from differently contaminated locations, i.e. the Kaštela Bay and the area around Šolta Island. For both locations hepatic MTs are comparable, but MT level in fish intestine is significantly higher in specimens from coastal urban area (Kaštela Bay) and is significantly associated with Cu (R=0.44). Therefore, MT induction in intestine cytosol has been regarded as Cu associated biochemical response in native red mullet specimens dwelling above sediments in the Kaštela Bay that have already been reported as elevated in Cu, as the consequence of anthropogenic activities.

biomarkers; ecotoxicology; metallothioneins; heavy metals; benthic fish

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