Diel rhythm in activity of antioxidant enzymes, as well as contents of glutathione and lipid peroxides, has been intensively investigated in Mammalia and Aves, however, the relevant studies about fish are few. In the present study, we examined variation in contents of cortisol, glucose and lactic acid in plasma of black sea bass Centropristis striata under natural photoperiod during a 24-h period. In addition, variation in activity of antioxidant enzymes, such as superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), catalase (CAT) and glutathione reductase (GR) as well as contents of total glutathione (T-GSH), reduced glutathione (GSH), oxidized glutathione (GSSG) and malondialdehyde (MDA) in liver and plasma of the fish were also determined. The plasma and liver samples were collected from the test fish at 3 h intervals during a 24-h cycle, with the first sampling time set at 03:00 h. No significant differences were found in glucose content and activities of GSH-PX and GR in plasma, as well as activities of SOD and GR in liver among different sampling times. In contrast, apparent variation was observed in contents of cortisol, lactic acid and MDA in plasma, activities of SOD and CAT in plasma, contents of MDA, T-GSH, GSH and GSSG in liver and activities of GSH-PX and CAT in liver between different sampling times. Moreover, contents of cortisol and MDA in plasma, SOD activity in plasma, and contents of MDA, GSH and GSSG in liver exhibited circadian rhythm, and their acrophases occurred at 06:08 h, 18:38 h, 15:09 h, 09:57 h, 23:36 h and 07:30 h, respectively. The present study indicates that some physiological parameters relating to stress response, such as cortisol and MDA contents in plasma, MDA, GSH and GSSG contents in liver and SOD activity in plasma changed at different time throughout a day in black sea bass. Therefore, caution should be taken when evaluating stress response in fish with these physiological parameters measured at different times.

中文翻译：

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天然光周期下黑鲈Centropristis striata的皮质醇，葡萄糖，乳酸和抗氧化系统的Diel变化

在哺乳动物和阿韦斯，人们对抗氧化酶活性以及谷胱甘肽和脂质过氧化物的狄尔节律进行了深入研究，但有关鱼类的相关研究很少。在本研究中，我们研究了在自然光周期下的24小时内黑鲈鲈的血浆中皮质醇，葡萄糖和乳酸含量的变化。此外，减少了抗氧化酶（如超氧化物歧化酶（SOD），谷胱甘肽过氧化物酶（GSH-PX），过氧化氢酶（CAT）和谷胱甘肽还原酶（GR））活性的变化以及总谷胱甘肽（T-GSH）的含量还测定了鱼肝和血浆中的谷胱甘肽（GSH），氧化型谷胱甘肽（GSSG）和丙二醛（MDA）。在24小时周期内，每隔3小时从测试鱼中收集血浆和肝脏样品，第一个采样时间设置为03:00 h。在不同采样时间之间，血浆中葡萄糖含量，GSH-PX和GR活性以及肝脏中SOD和GR活性均无显着差异。相反，血浆中皮质醇，乳酸和MDA的含量，血浆中SOD和CAT的活性，肝脏中MDA，T-GSH，GSH和GSSG的含量以及肝脏中GSH-PX和CAT的活性存在明显的变化。在不同的采样时间之间。此外，血浆中的皮质醇和MDA含量，血浆中的SOD活性以及肝脏中的MDA，GSH和GSSG含量均表现为昼夜节律，其顶相出现在06:08 h，18：38 h，15：09 h，09分别为：57小时，23：36小时和07:30小时。本研究表明，一些与应激反应有关的生理参数，在黑鲈中，血浆中的皮质醇和MDA含量，肝脏中的MDA，GSH和GSSG含量以及血浆中的SOD活性在一天中的不同时间发生变化。因此，在用不同时间测量的这些生理参数评估鱼的应激反应时应谨慎。