Departamento de Biologia Celular, Universidade de Brasília, Brasília, DF, Brazil; Área de Morfologia, Faculdade de Medicina, Universidade de Brasília, Brasília, DF, Brazil.
Departamento de Biologia Celular, Universidade de Brasília, Brasília, DF, Brazil; Laboratory of Adaptations to Extreme Environments and Global Change Biology, University College of Cundinamarca, Bogotá, Colombia.
Sci Total Environ. 2020 Jun 25;723:137957. doi: 10.1016/j.scitotenv.2020.137957. Epub 2020 Mar 14.
Preparation for oxidative stress (POS), i.e., the buildup of endogenous antioxidants during metabolic depression or low oxygen stress conditions, has been observed in at least 8 animal phyla under controlled conditions in laboratory. Despite the expected implications on the endurance to extreme environments and ecosystem occupation, the extent to which POS occurs in animals under natural conditions remains unexplored. Therefore, we took advantage of the natural history of the Brazilian Caatinga's frog Proceratophrys cristiceps to investigate the modulation of endogenous antioxidants and redox balance in their skeletal muscle and to verify if POS occurs under natural conditions. Expectedly, estivating frogs had low levels of the oxidative metabolism enzymes. Citrate synthase and isocitrate dehydrogenase activities were 36% and 25% lower than those in active frogs respectively. We found an overall upregulation of antioxidants in estivating P. cristiceps. Reduced glutathione concentration was 61% higher in estivating frogs than that in active animals. During estivation the activities of the hydroperoxide detoxification enzymes catalase, glutathione peroxidase, and glutathione HO-peroxidase were 48%, 57%, and 78% greater than those during the rainy season. Moreover, estivating frogs had a 47% lower ratio of disulfide to total glutathione levels than active frogs. Our findings confirm the occurrence of 'preparation for oxidative stress' in naturally estivating frogs and paves the way for further research on the redox biology of animals under natural settings. Such approach might reveal biochemical strategies under ecologically relevant scenarios.
在实验室的控制条件下，至少在 8 个动物门中观察到了氧化应激（POS）的准备，即在代谢抑制或低氧应激条件下，内源性抗氧化剂的积累。尽管这对极端环境和生态系统占据的耐力有预期的影响，但 POS 在自然条件下的动物中发生的程度仍未被探索。因此，我们利用巴西 Caatinga 的青蛙 Proceratophrys cristiceps 的自然历史，研究了内源性抗氧化剂和氧化还原平衡在其骨骼肌中的调节，并验证了 POS 是否在自然条件下发生。如预期的那样，休眠的青蛙的氧化代谢酶水平较低。柠檬酸合酶和异柠檬酸脱氢酶的活性分别比活跃的青蛙低 36%和 25%。我们发现休眠的 P. cristiceps 中抗氧化剂总体上调。与活跃动物相比，休眠青蛙中的还原型谷胱甘肽浓度高 61%。在休眠期间，过氧化氢解毒酶过氧化氢酶、谷胱甘肽过氧化物酶和谷胱甘肽过氧化物酶的活性比雨季高 48%、57%和 78%。此外，休眠的青蛙的二硫键与总谷胱甘肽水平的比值比活跃的青蛙低 47%。我们的发现证实了自然休眠青蛙中“氧化应激准备”的发生，并为在自然环境下研究动物的氧化还原生物学铺平了道路。这种方法可能揭示出在生态相关情景下的生化策略。
