engleski

Selenium in brown bears from Croatia: Relation to mercury and cadmium levels

Selenium (Se) is an essential trace element whose level in tissues depends on dietary intake and soil content. On the contrary, mercury (Hg) and cadmium (Cd) are considered ubiquitous environmental toxins known to accumulate in animal tissues. Selenoproteins and metabolites of Se are proposed to form a complex with Hg and Cd in the organism thereby protecting from harmful effects. This study was undertaken to investigate brown bear tissue levels of Se and a potential correlation with Hg and Cd. There are no published data on Se in Dinara-Pindos bear population of which Croatian bears are a part. Selenium, Hg and Cd were measured using inductively coupled plasma-mass spectrometry in muscle, liver and kidney cortex of 111 brown bears (Ursus arctos) hunted in Gorski kotar and Lika during 2009 and 2010 according to "The Brown Bear Management Plan for Croatia". The highest Se and toxic metal concentrations were found in kidney cortex. Distribution of Se across tissues was as follows (median ; range): muscle (0.139 ; 0.019-0.366 μg/g wet mass), liver (0.409 ; 0.029-0.814 μg/g), kidney (1.75 ; 0.203-2.23 μg/g). Females had higher Se in muscle (p<0.001) and kidney (p<0.05) than males. Tissue Se was associated with Cd in muscle (Spearman R=0.35) and kidney (R=0.43) (p<0.001), and more pronounced with Hg in all tissues (R=0.48-0.54, p<0.001). Unlike Cd and Hg, the variability of Se among tissues and bears is low due to homeostatic regulation. Observed correlations could be the consequence of Se co-accumulation with Cd and Hg but, because of relatively low level of toxic metals in bears, they are not very pronounced. Found Se levels in Croatian bear are in the range of reported muscle levels in Russian brown bear but lower than in polar bears.

brown bear; cadmium; mercury; selenium; tissue element level

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