Department of Biology, Faculty of Marine and Environmental Sciences, University of Cádiz, 11510 Puerto Real (Cádiz), Spain.
Gen Comp Endocrinol. 2011 Apr 1;171(2):203-10. doi: 10.1016/j.ygcen.2011.01.010. Epub 2011 Feb 1.
The hypothalamus-pituitary-interrenal (HPI) axis is pivotal in the endocrine stress response of fish. Hypothalamic corticotropin-releasing hormone (CRH) initiates the endocrine stress response and stimulates the release of adrenocorticotropic hormone (ACTH) from the pituitary pars distalis, which in turn activates cortisol production and release by the interrenal cells of the head kidney. CRH activity depends on the levels of a specific CRH binding protein (CRH-BP). We have characterized the cDNAs coding for CRH and CRH-BP in Senegalese sole (Solea senegalensis) and investigated their mRNA expression in juveniles that were submitted to a protocol that involved exposure to a chronic stressor (viz. increased cultivation densities) followed by an acute stressor (viz. transfer to increased ambient salinity). Juveniles were cultivated at three densities (1.9, 4.7 and 9.8 kg/m(2)) for 33 days, and then exposed to an osmotic challenge that involved transfer from seawater (39‰ salinity, SW) to hypersaline seawater (55‰, HSW). The highest density imposed stress as indicated by elevated cortisol levels and CRH mRNA expression compared to fish stocked at low density. Fish kept at high density differentially responded to a posterior transfer to HSW; no cortisol or CRH response was seen, but osmoregulatory and metabolic parameters were affected. No differences in CRH-BP mRNA expression levels were found at different stocking densities; transfer to HSW enhanced expression in both low and high density stocked animals, suggesting that CRH-BP acts as a modulator of the acute stress response, not so of the chronic stress response. We conclude that stocking of Senegalese sole at high density is a stressful condition that may compromise the capacity to cope with subsequent stressors.
下丘脑-垂体-肾上腺（HPI）轴是鱼类内分泌应激反应的关键。下丘脑促肾上腺皮质激素释放激素（CRH）启动内分泌应激反应，刺激垂体后叶促肾上腺皮质激素（ACTH）的释放，进而激活头肾间充质细胞的皮质醇产生和释放。CRH 活性取决于特定的 CRH 结合蛋白（CRH-BP）的水平。我们已经鉴定了塞内加尔比目鱼（Solea senegalensis）中编码 CRH 和 CRH-BP 的 cDNA，并研究了它们在幼鱼中的 mRNA 表达，这些幼鱼经历了一个涉及暴露于慢性应激源（即增加养殖密度）然后暴露于急性应激源（即转移到增加的环境盐度）的方案。幼鱼在三种密度（1.9、4.7 和 9.8 kg/m2）下养殖 33 天，然后暴露于渗透压挑战，从海水（39‰盐度，SW）转移到高盐海水（55‰，HSW）。与低密度养殖的鱼类相比，最高密度组的皮质醇水平和 CRH mRNA 表达升高，表明其受到应激。高密度养殖的鱼类对随后转移到 HSW 有不同的反应；没有观察到皮质醇或 CRH 反应，但渗透调节和代谢参数受到影响。在不同的养殖密度下，CRH-BP mRNA 表达水平没有差异；转移到 HSW 增强了低和高密度养殖动物的表达，表明 CRH-BP 是急性应激反应的调节剂，而不是慢性应激反应的调节剂。我们得出结论，高密度养殖塞内加尔比目鱼是一种应激条件，可能会影响其应对后续应激源的能力。
