АКТИВНОСТЬ ФЕРМЕНТОВ ЭНЕРГЕТИЧЕСКОГО ОБМЕНА И СОДЕРЖАНИЕ АТФ В ТКАНЯХ МОЗГА И ЖАБР МОРСКОГО ЕРША SCORPAENA PORCUS LINNAEUS ПРИ КРАТКОВРЕМЕННОЙ ГИПОКСИИ

The effect of short-term hypoxia on the activity of oxidoreductases – malate dehydrogenase (MDH, 1.1.1.37) and lactate dehydrogenase (LDH, 1.1.1.27) in the scorpaena organs determining an urgent adaptation to oxygen deficiency – brain and gills (first branchial arch) was studied. The control group of fish was exposed to 4.5–6.7 mg O2  L –1 (normoxia), experimental groups were kept under 1.7–3.7 mg O2  L –1  (mild hypoxia) and to 0.3–1.0 mg O2  L –1 (acute hypoxia). The oxygen content in the water was reduced by saturating it with nitrogen. All groups of fish were ex- posed to examined condition during 90 min under 21–22 ° С. It was shown that hypoxia had not a significant im- pact on the brain structures of scorpaena. Under acute hypoxia MDH, LDH activity, MDH/LDH index and ATP content in forebrain, diencephalon, midbrain (FDMB) and medulla (MB) remained at the level of control values. Mild hypoxia caused a proportional rise of MDH, LDH activity and increased ATP level in FDMB like a consequence of the reducing need in ATP in these brain area. Above-mentioned phenomenon could be based on the GABA-ergic mechanism of the regulation of brain tissue activity that is able to reduce the energetic needs of the nervous tissue through the increased density in GABA A  receptor apparatus. The gill tissue had a minimal activity of MDH, LDH on the background of high MDH/LDH index value. Acute hypoxia was accompanied by the drop in LDH activity and increased MDH/LDH which was related to anaerobic mode of operation in gill tissue. Under acute hypoxia there was an increase in the relationship in “MDH activity  ↔  LDH activity” system (r = 0.81–0.94, p < 0.05–0.01) in all types of tissues, which is typical for the species tolerant to oxygen deficiency. Probably, this effect is achieved by the conjugation of MDH with glycolysis substrates in the conditions of acute O 2  deficiency, which excludes the accumulation of lactate during metabolic depression.