Exposure to high temperatures induces changes in fish respiration, resulting in an increased production of reactive oxygen species. This, in turn, affects the enzymatic and non-enzymatic components of antioxidant defenses, which are essential for mitigating cellular stress. Rhamdia voulezi, an economically important fish species endemic to Brazil’s Iguaçu River, served as the subject of our study. Our goal was to assess enzymatic antioxidant biomarkers (superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase, glutathione reductase, glucose-6-phosphate dehydrogenase), non-protein thiol levels (reduced glutathione), and markers of oxidative damage (lipoperoxidation and carbonylation) in the liver, gills, and kidneys of R. voulezi after acute exposure to high temperatures (31°C) for 2, 6, 12, 24, and 96 h. Control groups were maintained at 21°C. Our findings revealed that the liver exhibited increased superoxide dismutase levels up to 12 h and elevated glutathione S-transferase levels at 12 and 96 h at 31°C. In the gills, superoxide dismutase levels increased up to 24 h, along with increased lipoperoxidation at 2, 6, 12, and 96 h of exposure to high temperatures. The kidneys responded to heat stress at 12 h, with an increase in superoxide dismutase and catalase activity, and lipid peroxidation was observed at 2 and 6 h at 31°C. The three tissues evaluated responded differently to heat stress, with the liver demonstrating greater physiological adjustment to high temperatures. The intricate interplay of various antioxidant defense biomarkers and oxidative damage suggests the presence of oxidative stress in R. voulezi when exposed to high temperatures.

暴露在高温下会引起鱼类呼吸的变化，导致活性氧的产生增加。这反过来又影响抗氧化防御的酶和非酶成分，这对于减轻细胞压力至关重要。Rhamdia voulezi是巴西伊瓜苏河特有的一种重要经济鱼类，也是我们研究的对象。我们的目标是评估酶抗氧化生物标志物（超氧化物歧化酶、过氧化氢酶、谷胱甘肽过氧化物酶、谷胱甘肽 S-转移酶、谷胱甘肽还原酶、6-磷酸葡萄糖脱氢酶）、非蛋白硫醇水平（还原型谷胱甘肽）和氧化损伤标志物（脂过氧化）急性暴露于高温 (31°C) 2、6、12、24 和 96 小时后，R. voulezi的肝脏、鳃和肾脏中的碳酰化和羰基化） 。对照组维持在21°C。我们的研究结果显示，在 31°C 下，肝脏在长达 12 小时内表现出超氧化物歧化酶水平升高，并在 12 小时和 96 小时内表现出谷胱甘肽 S-转移酶水平升高。在鳃中，超氧化物歧化酶水平增加长达 24 小时，同时暴露于高温 2、6、12 和 96 小时时脂过氧化作用增加。肾脏在 12 小时对热应激做出反应，超氧化物歧化酶和过氧化氢酶活性增加，并且在 31°C 2 小时和 6 小时观察到脂质过氧化。所评估的三种组织对热应激的反应不同，肝脏对高温表现出更大的生理调节。各种抗氧化防御生物标志物和氧化损伤之间错综复杂的相互作用表明，当暴露于高温时，R. voulezi中存在氧化应激。