Vera Luisa María, Montoya Ander, Pujante Isabel M, Pérez-Sánchez Jaume, Calduch-Giner Josep Alvar, Mancera Juan Miguel, Moliner Javier, Sánchez-Vázquez F J
Department of Physiology, Faculty of Biology, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia , Murcia , Spain .
Chronobiol Int. 2014 Nov;31(9):1051-61. doi: 10.3109/07420528.2014.945646. Epub 2014 Aug 7.
Since fish show daily rhythms in most physiological functions, it should not be surprising that stressors may have different effects depending on the timing of exposure. In this study, we investigated the influence of time of day on the stress responses, at both physiological and cellular levels, in gilthead sea bream (Sparus aurata L.) submitted to air exposure for 30 s and then returned to their tank. One hour after air exposure, blood, hypothalamus and liver samples were taken. Six fish per experimental group (control and stressed) were sampled every 4 h during a 24-h cycle. Fish were fed in the middle of the light cycle (ML) and locomotor activity rhythms were recorded using infrared photocells to determine their daily activity pattern of behaviour, which showed a peak around feeding time in all fish. In the control group, cortisol levels did not show daily rhythmicity, whereas in the stressed fish, a daily rhythm of plasma cortisol was observed, being the average values higher than in the control group, with increased differences during the dark phase. Blood glucose showed daily rhythmicity in the control group but not in the stressed one which also showed higher values at all sampling points. In the hypothalamus of control fish, a daily rhythm of corticotropin-releasing hormone (crh) gene expression was observed, with the acrophase at the beginning of the light phase. However, in the stressed fish, this rhythm was abolished. The expression of crh-binding protein (crhbp) showed a peak at the end of the dark phase in the control group, whereas in the stressed sea bream, this peak was found at ML. Regarding hepatic gene expression of oxidative stress biomarkers: (i) cytochrome c oxidase 4 showed daily rhythmicity in both control and stressed fish, with the acrophases located around ML, (ii) peroxiredoxin (prdx) 3 and 5 (prdx5) only presented daily rhythmicity of expression in the stressed fish, with the acrophase located at the beginning of the light cycle and (iii) uncoupling protein 1 showed significant differences between sampling points only in the control group, with significantly higher expression at the beginning of the dark phase. Taken together, these results indicate that stress response in gilthead sea bream is time-dependent as cortisol level rose higher at night, and that different rhythmic mechanisms interplay in the control of neuroendocrine and cellular stress responses.
由于鱼类的大多数生理功能都呈现出日节律，因此应激源可能会因暴露时间的不同而产生不同影响，这并不奇怪。在本研究中，我们调查了一天中的不同时间对金头鲷（Sparus aurata L.）生理和细胞水平应激反应的影响，将金头鲷暴露于空气中30秒后放回水箱。暴露于空气1小时后，采集血液、下丘脑和肝脏样本。在24小时周期内，每4小时对每个实验组（对照组和应激组）的6条鱼进行采样。在光照周期的中间时段（ML）给鱼喂食，并使用红外光电管记录运动活动节律，以确定它们的日常行为活动模式，所有鱼在喂食时间左右均出现活动高峰。在对照组中，皮质醇水平未呈现日节律，而在应激鱼中，观察到血浆皮质醇的日节律，其平均值高于对照组，在黑暗期差异增大。血糖在对照组中呈现日节律，而在应激组中未呈现，且在所有采样点应激组的值均更高。在对照鱼的下丘脑中，观察到促肾上腺皮质激素释放激素（crh）基因表达的日节律，其高峰期在光照期开始时。然而，在应激鱼中，这种节律被消除。crh结合蛋白（crhbp）的表达在对照组黑暗期结束时出现峰值，而在应激金头鲷中，该峰值出现在ML。关于氧化应激生物标志物的肝脏基因表达：（i）细胞色素c氧化酶4在对照鱼和应激鱼中均呈现日节律，高峰期位于ML左右；（ii）过氧化物酶（prdx）3和5（prdx5）仅在应激鱼中呈现表达的日节律，高峰期位于光照周期开始时；（iii）解偶联蛋白1仅在对照组的采样点之间存在显著差异，在黑暗期开始时表达显著更高。综上所述，这些结果表明，金头鲷的应激反应具有时间依赖性，因为夜间皮质醇水平升得更高，并且不同的节律机制在神经内分泌和细胞应激反应的控制中相互作用。
