АКТИВНОСТЬ ОКСИДОРЕДУКТАЗ В ОКСИФИЛЬНЫХ ТКАНЯХ МОРСКОГО ЕРША SCORPAENA PORCUS LINNAEUS, 1758 ПРИ КРАТКОСРОЧНОЙ СЕРОВОДОРОДНОЙ НАГРУЗКЕ

Hydrogen sulfide can exert a toxic effect and also function as a signaling molecule in various physiological processes. Under conditions of short-term experimental hydrogen sulfide loading (HSL), activities of oxidoreductases (enzymes of energy metabolism and antioxidant defense) - malate dehydrogenase (MDH, 1.1.1.37), lactate dehydrogenase (LDH, 1.1.1.27), catalase (1.11.1.6) – were analyzed in oxyphilic tissues (brain, heart, gills) of the Black Sea scorpionfish Scorpaena porcus Linnaeus, 1758. Two groups of fish were exposed for 5 min to different concentrations of sodium sulfide (37 and 75 μM Na2S) used as a hydrogen sulfide donor. High MDH and LDH activities were detected in the brain structures and heart chambers, reflecting a similar potential of energy metabolism in these tissues, while enhanced LDH activity in the brain indicated anaerobization of the energy metabolism pathways. Differences in oxydoreductase activities were found between the first and fourth branchialarches, heart atrium and ventricle, as well as between different brain compartments. Under HSL, the gills exhibited some signs of hypoxemia (increasing darkening of the lamellae as the Na2S concentration moved upward) and metabolic depression. At a low Na2S concentration, HSL did not cause significant changes in oxidoreductase activities in the brain and heart, while upon a 2-fold increase in the concentration these changes became more pronounced. In the key oxyphilic structures (anterior brain compartments, heart ventricle) intense HSL led to a simultaneous increase in LDH and MDH activities, which was due to the ability of MDH to participate in anaerobic processes. The less O2-sensitive structures (medulla oblongata and heart atrium) exhibited almost no changes in MDH and LDH activities even in response to high-intensity HSL, suggesting a different mode of energy metabolism in these tissues. Under intense HSL, the oxidoreductases in the heart ventricles and anterior brain compartments demonstrated responses, which were similar to those under hypoxia/anoxia.