Laboratory for Ecophysiology, Biochemistry and Toxicology, University of Antwerp, Antwerp, Belgium.
Aquat Toxicol. 2012 Oct 15;122-123:93-105. doi: 10.1016/j.aquatox.2012.05.013. Epub 2012 Jun 7.
Waterborne ammonia has become a persistent pollutant of aquatic habitats. During certain periods (e.g. winter), food deprivation may occur simultaneously in natural water. Additionally, under such stressful circumstances, fish may be enforced to swim at a high speed in order to catch prey, avoid predators and so on. Consequently, fish need to cope with all these stressors by altering physiological processes which in turn are controlled by their genes. In this present study, toxicogenomic analyses using real time PCR was used to characterize expression patterns of potential biomarker genes controlling growth, ion regulation and stress responses in common carp subjected to elevated ammonia (1 mg/L; Flemish water quality guideline for surface water) following periods of feeding (2% body weight) and fasting (unfed for 7 days prior to sampling). Both feeding groups of fish were exposed to high environment ammonia (HEA) for 0 h (control), 3h, 12h, 1 day, 4 days, 10 days, 21 days and 28 days, and were sampled after performing swimming at different speeds (routine versus exhaustive). Results show that the activity and expression of Na(+)/K(+)-ATPase, an important branchial ion regulatory enzyme, was increased after 4-10 days of exposure. Effect of HEA was also evident on expression patterns of other ion-regulatory hormone and receptor genes; prolactin and cortisol receptor mRNA level(s) were down-regulated and up-regulated respectively after 4, 10 and 21 days. Starvation and exhaustive swimming, the additional challenges in present study significantly further enhanced the HEA effect on the expression of these two genes. mRNA transcript of growth regulating hormone and receptor genes such as Insulin-like growth factor I, growth hormone receptor, and the thyroid hormone receptor were reduced in response to HEA and the effect of ammonia was exacerbated in starved fish, with levels that were remarkably reduced compared to fed exposed fish. However, the expression of the growth hormone gene itself was up-regulated under the same conditions. Expression of somatolactin remained unaltered. Stress representative genes, cytochrome oxidase subunit 1 showed an up-regulation in response to HEA and starvation while the mRNA level of heat shock protein 70 was increased in response to all the three stressors. The expression kinetics of the studied genes could permit to develop a "molecular biomarker system" to identify the underlying physiological processes and impact of these stressors before effects at population level occur.
水中氨已成为水生栖息地的一种持久性污染物。在某些时期（例如冬季），天然水中可能会同时发生食物短缺。此外，在这种压力情况下，鱼类可能被迫高速游动以捕食猎物、躲避捕食者等。因此，鱼类需要通过改变生理过程来应对所有这些压力，而这些过程反过来又受到它们的基因控制。在本研究中，使用实时 PCR 的毒理基因组学分析用于描述在喂食（体重的 2%）和禁食（在采样前禁食 7 天）后，鲤鱼中控制生长、离子调节和应激反应的潜在生物标志物基因的表达模式，然后将其暴露于升高的氨（1mg/L；佛兰德地表水水质指南）中。两组摄食的鱼都在高环境氨（HEA）中暴露 0h（对照）、3h、12h、1 天、4 天、10 天、21 天和 28 天，然后在以不同速度（常规与耗尽）游泳后取样。结果表明，Na(+)/K(+)-ATPase 的活性和表达在暴露 4-10 天后增加。HEA 的作用也表现在其他离子调节激素和受体基因的表达模式上；催乳素和皮质醇受体 mRNA 水平分别在 4、10 和 21 天后下调和上调。在本研究中，饥饿和耗尽游泳这两个额外的挑战显著进一步增强了 HEA 对这两个基因表达的影响。胰岛素样生长因子 I、生长激素受体和甲状腺激素受体等生长调节激素和受体基因的 mRNA 转录物对 HEA 的反应减少，并且在饥饿鱼类中氨的作用加剧，与暴露于食物的鱼类相比，水平明显降低。然而，在相同条件下，生长激素基因本身的表达上调。生长激素基因的表达保持不变。应激代表基因细胞色素氧化酶亚基 1 对 HEA 和饥饿的反应上调，而热休克蛋白 70 的 mRNA 水平在所有三种应激源的反应中都增加。所研究基因的表达动力学可以开发一种“分子生物标志物系统”，以便在种群水平出现影响之前，识别这些压力源的潜在生理过程和影响。
