Features of nitrogen metabolism in fishes

Presence in water is easily metabolized nitrogen-containing substances is a vital condition for the existence of food organisms in ponds used for fish reproduction. At the same time, the end products of nitrogen metabolism—ammonia, nitrites and nitrates are always displayed the body of fish into the environment, adding to the total number of these compounds dissolved in water. Ammonia, nitrite and nitrate anions are formed during biological processes, as well as man-made origin, have toxic properties and are considered as environmental factors that may limit fish productivity of reservoirs. The results of a brief review of the literature showed that the features of nitrogen metabolism in fish are actual direction of research, both theoretical science and in practical fish farming. Published the results of studies of amino acid metabolism in fish suggest that, firstly, the processes responsible for the neutralization and the release of ammonia from the body of fish, as well as ontogenetic aspects of the dynamics of formation and emission of ammonia is not fully understood. Meanwhile, several authors stressed the importance of this area of interest for the formation of science-based ways to improve the efficiency of plant breeding in fish culture. Secondly, endogenous nitrite, being the product of oxidation of the molecule nitric oxide and its transport form, the norm are always present in fish. However, the mechanisms responsible for maintaining the stability of the concentration of nitrite in the internal environment of fish, not well understood. Also, in our opinion, of interest to determine the physiological rules of nitrites and nitrates in the body of various species, depending on the seasons and stages of ontogeny. Thirdly, the literature pays much attention to the toxic properties of nitrite in water biocenosis. Certainly, the analysis of the manifestation in fish tissue-specific toxic effects of nitrites and their derivatives—an important area of research. Nevertheless, we can not exclude that it may be quite promising analysis of the incorporation of exogenous nitrite as a substrate exist in fish of the physiological mechanisms re-synthesis of nitric oxide. This kind of “interference” of endogenous and exogenous nitrite-anions are not causing serious structural damage to organs and tissues, however, can cause substantial damage to the practical fish farming, causing changes in the level of regulatory mechanisms of fish at the most critical stages: when working with manufacturers, the incubation of eggs, and larvae rearing and wintering fish.
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