Effects of cadmium and copper on sialic acid levels in blood and brain tissues of Cyprinus carpio L

Sialic acids (N-acetylneuraminic acids) are negatively charged monosaccharides which are common constituents in oligosaccharides of vertebrates and some invertebrate species[1]. They are possibly the most biologically important monosaccharide units of glycoconjugates. The majority of sialic acid in higher animals is bound up in glycoconjugates. Sialic acid often occurs as the terminal monosaccharide of oligosaccharide chains of glycoproteins, glycosphingolipids and glycophosphatidylinositol anchors. Both its negative charge and its terminal position make it critical in numerous biological processes. Sialic acids impart a net negative charge to the cell surface and are important in cell-to-cell and cell-to-matrix interactions. Because sialic acids have got negative charge, heavy metals (positive ions) such as copper (Cu) and cadmium (Cd) might affected sialic acids levels on different tissues. Quantitative and qualitative differences in sialic acid are seen in health and disease and at different stages of cell growth, differentiation, aging and malignant transformation[2]. In recent years, it has been reported that levels of sialic acid are increased in certain types of cancer[3], and it has been proposed that sialic acid may be a useful tumor marker for some cancer types[4]. ARTICLE INFO ABSTRACT