Level of oxidative processes and total lipids in immunocompetent organs of bream of the Saratov reservoir

Data on the level of oxidative processes and antioxidant defence in tissues of hydrobionts are often used as biomarkers in ecological and ecological-toxicological studies to assess the quality of habitat conditions. In the present work, the intensity of oxidative processes and the content of total lipids in immunocompetent organs of sexually mature bream from the central part and lower reaches of the Saratov reservoir were determined. Fish were caught using bottom trawls during a complex hydrobiological expedition on a research vessel. Samples of kidney, spleen and liver were taken from captured individuals after autopsy into sterile tubes. Homogenates were prepared from organ tissues using a homogeniser with 0.65% physiological solution at a ratio of 1:6 and 1:1 (weight to volume). The content of peroxidation products in homogenates was analysed by malonic dialdehyde content, level of antioxidant activity and total lipids. Analysis of the results showed that bream caught at different stations differed significantly in the quantitative indices of malonic dialdehyde and antioxidant activity and not significantly in the amount of total lipids. The lowest level of malonic dialdehyde was observed in the organs of fish from Kashpir-Rudnik station, compared to individuals from other stations. The revealed differences in the intensity of oxidative processes in immunocompetent organs are probably due to different levels of antioxidant enzymes and low molecular weight compounds providing dynamic equilibrium in the pro-oxidant-antioxidant system. This is probably related to the impact on the fish organism of various environmental factors and water quality in the studied areas of the Saratov Reservoir. The difference in water quality is most likely due to the mass development of bluegreen algae (‘blooming’ of water), the biomass of which increases in the direction from the upper section of the reservoir to the lower one.