Influence of fluctuations the hydrothermal regime in the system “reservoir – hydroelectric complex – tailwater pool of the river” on the state of lipoperoxidation and the activity of antioxidant defense system in brain tissues of the Siberian sturgeon was investigated in aquarium conditions. Experimental modeling of the flush of “warm” water from the reservoir into the tailwater pool of the river showed the important role of free radical mechanisms in the realization of ecotoxicological effects in the water of the dam site of hydroelectric power station.
Streamlining of river drains by dams of hydroelectric power plants causes the profound transformations in environment and promotes emergence of environmental problems  that leads to a decrease in number of commercial fish population [2, 4]. In accordance to classical concepts of Environmental Toxicology, the decreasing of number of living organisms, as well as rising of their quantity is a sign of the ecotoxicity . It is considered that fluctuations of hydrothermal regime in the system “reservoir – hydroelectric complex – tailwater pool of the river” is a factor of ecotoxicity in water areas of many rivers . Mechanisms of implementation the ecotoxic effect in such systems are still poorly explored. In this case, the development and use of experimental models which reproduce fluctuations of the hydrothermal regime and allow observing a condition of fish is a prospective approach. It studies the ecotoxicological problems of the construction and operation of dams at hydroelectric power plants.
The purpose of this research was to study the influence of fluctuations the hydrothermal regime on a state of lipoperoxidation and the activity of antioxidant protection system in brain tissues of the Siberian sturgeon.
Material and methods of research. The research was carried out in the Laboratory of Reproduction of Aquatic Biological Resources on the young fish of Siberian sturgeon during Autumn-Winter period of 2009–2013.
20 Sturgeons of control group were in aquarium filled with water of constant temperature 17,2 ± 0.57 ºС. 20 fishes of experimental group were in aquarium with temperature fluctuations every 24-hours as it takes place in natural environment. Fluctuation of the hydrothermal regime of water was carried out by sequentially increasing and decreasing the temperature on 5 ± 0,57 ºС relatively to 17,2 ºС. Experimental modeling of the flush of warm water took place during two hours at three times per 24-hours for one month. Fishes of all groups were removed from experiment through 30 days of observation.
The important role of free radical processes in brain tissues evaluates by the methods of biochemical analysis. Structural characteristics of brain tissues tested by methods of morphological analysis using the light optical (microscope CARL ZEISS Axio Imager M2, Germany) and the ultrastructural levels (electronic microscope JEM-1400 “Jeol” Japan).
Results of research and their discussion. Difficulties of metabolic processes in brain tissues of the Siberian sturgeon were found during modeling of the impact of fluctuations of hydrothermal regime on the organism of fish. This is evidence by changes the biochemical indexes of lipoperoxidation and activity of antioxidant protective system. Sturgeons of experimental group had increase diene conjugates and catalase activity than in control samples. At the same time a quantity of malondialdehyde and activity of superoxide dismutase had decrease. This was the reason to suppose that the brain cells of experimental group’ fishes during the process of adaptation to temperature fluctuations continue to provide the inactivation of toxic hydroperoxides. During testing the samples of front part of brain of Sturgeons from experimental group in laboratory by the light microscope were found signs of water-ion homeostasis in ependimoglia and neuropil. Results of morphological testing show that these Sturgeons had a structural disruption, including ependimoglia functions.
Using the electronic microscope we found that neuron structure of front part of brain of the experimental group is different from the control samples. A wide lucidity in the cistern of endoplasmatic reticulum and Golgy apparatus are in cytoplasm of neuron. Compared with the control of neuron in cytoplasm of experimental group fishes the quantity of lysosomes and phagosomes are increased. Regularity in all studied samples of brain of the fish showed violating the structure of myelin of different levels in neurons.
The set of identified morphological changes proved that the long-term temperature fluctuations lead to structural changes in grey and white stuff in brain of the Siberian sturgeon. Results showed that the temperature fluctuations accompanied with changing the level of synthetic processes which provide the antiradical protection of brain cells. The revealed free radical mechanism can testify to its key role in decreasing the number of sturgeon in streamlined river drains of dams of hydroelectric power plants.
The work is submitted to the International Scientific Conference “Fundamental and applied research in medicine”, France, Paris, October 14–21, 2014 came to the editorial office оn 12.09.2014.