RESUMO
OBJECTIVE: Ectothermic fish are directly affected by temperature changes in the environment. The aim of this study was to evaluate the metabolic responses in the gills of Yellowtail Lambari Astyanax lacustris under thermal stress. METHODS: To this end, we used spectrophotometry to evaluate the biomarkers of carbohydrate and protein metabolism, antioxidant defense, and oxidative damage in fish subjected to low (15°C) and high (31°C) temperatures, with control groups held at 23°C, for 2, 6, 12, 24, 48, and 96 h. RESULT: The results showed that cold thermal stress did not change the energy demand, and the antioxidant defense was reduced; therefore, the gills were vulnerable to the action of reactive oxygen species (ROS), presenting increased protein carbonylation at 12 h. With heat thermal stress, a higher energy demand was observed, which was verified by an increase in aerobic metabolism by glycolysis and the citric acid cycle. High-temperature stress also increased the antioxidant defenses, as verified by the increased activities of glutathione peroxidase, glutathione reductase, and glutathione S-transferase. However, the antioxidant defense system could not protect tissues from the action of ROS, as protein carbonylation increased at 6 and 24 h, indicating oxidative stress. CONCLUSION: The results showed that (1) temperature variations caused metabolic adjustments in the gills of Yellowtail Lambari, (2) the adaptive responses were different for winter and summer temperatures, and (3) Yellowtail Lambari recovered homeostasis when subjected to thermal stress, even with the occurrence of oxidative stress.
Assuntos
Antioxidantes , Perciformes , Animais , Antioxidantes/metabolismo , Temperatura , Espécies Reativas de Oxigênio/metabolismo , Catalase/metabolismo , Brânquias , Superóxido Dismutase/metabolismo , Estresse Oxidativo/fisiologia , Peixes/metabolismo , Glutationa Transferase/metabolismoRESUMO
Temperature is an important factor that conditions the physiological responses of fish, generating a stressful condition when in non-ideal parameters. Thus, the objective was to evaluate metabolic aspects in the muscle of fish Astyanax lacustris submitted to thermal shock. The specimens were subjected to 2, 6, 12, 24, 48, and 96 h of exposure to 15 °C and 31 1 °C, with their respective controls 23 °C. At 15 °C there was a reduction in glycogenolysis in the initial periods indicated by changes in glycogen phosphorylase (GP), pyruvate and lactate. Subsequently, there was an increase in GP activity, pyruvate levels and hexokinase activity in the next time periods, suggesting an increase in energy demand. At 31 °C there was observed low need for the protein metabolism, indicated by reduction in the activity of aspartate aminotransferase and alanine aminotransferase. At 15 °C, initial periods show an increase in glutathione reductase activity and an increase in carbonylated protein levels, indicating induction of oxidative stress for muscle. At 31 °C, there was a punctual increase in reduced glutathione levels at 24 h. In addition, the integrated biomarker response index proved to be a good ally in the evaluation of a set of biomarkers, corroborating the results observed by the biomarkers individually. Thus, it is possible to conclude that the acute thermal shock affects the metabolism of A. lacustris muscle, which undergoes rearrangements to deal with temperature, where 15 °C is more stressful than 31 °C.
Assuntos
Antioxidantes , Músculos , Animais , Músculos/metabolismo , Antioxidantes/metabolismo , Estresse Oxidativo , Metabolismo dos Carboidratos , Biomarcadores/metabolismoRESUMO
Predictions about global warming have raised interest in assessing whether ectothermic organisms will be able to adapt to these changes. Understanding the physiological mechanisms and metabolic adjustment capacity of fish subjected to heat stress can provide subsidies that may contribute to decision-making in relation to ecosystems and organisms subjected to global climate change. This study investigated the antioxidant defence system and energy metabolism of carbohydrate and protein responses in the gill, liver and kidney tissues of Psalidodon bifasciatus (Garavello & Sampaio 2010), a Brazilian freshwater fish used in aquaculture and in biological studies, following exposure to heat shock at 31°C for 2, 6, 12, 24 and 48 h. The fish presented signs of stress in all tissues tested, as evidenced by increased lipid peroxidation concentration at 2 h and phosphofructokinase, hexokinase and malate dehydrogenase activity at 48 h in the gills; increased glutathione-S-transferase activity at 12 h, citrate synthase activity at 24 h and concentration of reduced glutathione (GSH) concentration at 12 and 48 h in the liver; and through increased activity of superoxide dismutase at 48 h, glutathione reductase at 24 h, glucose-6-phosphate dehydrogenase at 48 h and concentration of GSH at 24 h in the kidney. In the kidneys, changes in the antioxidant system were more prominent, whereas in the gills, there were greater changes in the carbohydrate metabolism. These results indicated the importance of glycolysis and aerobic metabolism in the gills, aerobic metabolism in the liver and pentose-phosphate pathway in the kidneys during homeostasis. The biomarker response was tissue specific, with the greatest number of biomarkers altered in the gills, followed by those in the kidneys and liver.
Assuntos
Antioxidantes , Characidae , Animais , Antioxidantes/metabolismo , Antioxidantes/farmacologia , Characidae/metabolismo , Ecossistema , Metabolismo Energético , Brânquias/metabolismo , Glutationa/metabolismo , Glutationa/farmacologia , Glutationa Peroxidase/metabolismo , Glutationa Peroxidase/farmacologia , Resposta ao Choque Térmico , Peroxidação de Lipídeos , Fígado/metabolismo , Estresse Oxidativo , Superóxido Dismutase/metabolismo , Superóxido Dismutase/farmacologiaRESUMO
Subtropical fish are exposed to seasonal variations in temperature that impose a set of adaptations on their metabolism necessary for the maintenance of homeostasis. In this study, we addressed the effects of temperature variation on the metabolism of Astyanax lacustris, a species of freshwater fish common in the subtropical region of Brazil. Biomarkers of carbohydrate and protein metabolism, antioxidant defense, and oxidative damage were evaluated in the liver of A. lacustris exposed to low (15 °C) and high (31 °C) temperature thermal shock, with controls at 23 °C for 2, 6, 12, 24, 48, 72, and 96 h. A high energy demand was observed during the first 48 h of exposure to 15 °C, which is necessary for metabolic adjustment at low temperatures, with an increase in glycolysis, citric acid cycle, and amino acid catabolism. In addition, at 31 °C, glucose was exported in the first 12 h of exposure, and an increase in the citric acid cycle suggested acetyl-CoA as the pathway substrate, originating from the oxidation of lipids. The antioxidant defenses did not change at 15 °C, as opposed to 31 °C, in which there were changes in several antioxidant defense markers, indicating a response to the production of ROS. However, oxidative stress was observed at both temperatures, with oxidative damage detected by lipid peroxidation at 15 °C and protein carbonylation at 31 °C.