Parametri antioksidacione zaštite u tkivima nekih vrsta slatkovodnih riba iz jezera Gruža
Antioxidant defence parameters in tissues of some species of freshwater fish from the Gruža reservoir
Doctoral thesis (Published version)
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Since fish can be directly exposed to cyanobacterial toxins, they are very good models to study the influence of cyanotoxins on the cellular antioxidant defence system. There is much information on biochemical and ultrastructural alterations in different fish tissues after exposure to cyanotoxins under laboratory conditions, however, data on the effects of cyanobacterial blooms in natural conditions are very scarce. The aim of this doctoral dissertation was to investigate the influence of the cyanobacterial bloom in the Gruža Reservoir on the antioxidant defence parameters in the liver, gills and muscle of freshwater fish Rutilus rutilus (roach), Blicca bjoerkna (white bream), Carassius gibelio (prussian carp) and Perca fluviatilis (European perch). The activity of antioxidant defence enzymes: total, manganese and copper zinc containing superoxide dismutases (Tot SOD, Mn SOD, CuZn SOD, EC 18.104.22.168), catalase (CAT, EC 22.214.171.124), glutathione peroxidase (GSH-Px, EC 126.96.36.199), glutathione reductase (GR, EC 188.8.131.52) and the biotransformation phase II enzyme glutathione-S-transferase (GST, EC 184.108.40.206), as well as the concentrations of total glutathione (GSH) and sulphydryl (SH) groups were determined. Histopathological examination of fish liver was performed by light and electron microscopy. All investigated parameters were measured before and during cyanobacterial bloom. The activities of Tot SOD and CuZn SOD in the liver of B. bjoerkna, as well as Mn SOD activity in the liver of all investigated fish species increased during the cyanobacterial bloom. Electrophoretic analysis of SOD revealed the presence of inducible SOD isoforms in the liver of B. bjoerkna during the bloom period. The activities of Tot SOD, CuZn SOD and Mn SOD in the gills and muscle of the investigated species exhibited different degrees of reduction during the cyanobacterial bloom. The activity of CAT in the liver of all investigated fish species was significantly lower during the bloom period than in the pre-bloom period. The opposite trend was detected in the gills of R. rutilus and P. fluviatilis, as well as in the muscle of all four fish species. Reduction in the enzymatic activity of GSH-Px in the liver and muscle of all investigated species and in the gills of B. bjoerkna and C. gibelio during the cyanobacterial bloom indicates that cyanotoxins impair the integrity of the cell membranes in all examined tissues. The activity of GR diminished significantly in the liver of C. gibelio, the gills of all four fish species, and in the muscle of R. rutilus and C. gibelio. The increase in the activity of the biotransformation phase II enzyme GST in the liver of B. bjoerkna during the bloom period points to a potential activation of the detoxification process of cyanobacterial toxins. The decrease in GST activity in the gills and muscle of all tested species indicates a perturbed efficiency of these tissues to conjugate cyanotoxins, which could lead to their intracellular accumulation during the cyanobacterial bloom. The concentrations of total GSH and SH groups exhibited a tissue- and species-dependent response. Ultrastructural examinations showed that hepatocytes displayed profound changes in almost all organelles during the cyanobacterial bloom. Some hepatocytes showed signs of necrosis, while propidiumiodide staining revealed that the bloom period also induced apoptotic changes in the liver of all investigated fish species. The presented results show that the cyanobacterial bloom-induced response to oxidative stress caused ultrastructural alterations in the liver. The results of this doctoral dissertation are a first report on the influence of the cyanobacterial bloom in the Gruža Reservoir on antioxidant defence parameters (SOD, CAT, GSH-Px, GR and biotransformation phase II enzyme GST activities, as well as concentrations of GSH and SH groups) in the liver, gills and muscle of freshwater fish Rutilus rutilus, Blicca bjoerkna, Carassius gibelio and Perca fluviatilis. Biomonitoring of antioxidant biomarkers in fish tissue could serve as an early warning signal of cellular damage resulting from exposure to cyanotoxins in freshwater ecosystems. This dissertation is an important contribution in the field of ecophysiology of aquatic organisms.
Keywords:Antioxidant defence parameters; Freshwater fish; Liver; Gills; Muscle; Cyanobacterial bloom; Gruža reservoir
Source:University of Belgrade, Faculty of Biology, 2012, 1-212
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