Role of cortisol in the physiological response to toxicants in fish

当生物体暴露于潜在的有害刺激时，会引起生理应激反应。皮质醇是鱼类组织水平反应的关键激素效应物。压力反应的特点是许多物种和不同的压力源，包括有毒物质，但关键的基本问题仍然存在：压力反应是有益的或有害的有机体在暴露于有毒物质;是脆弱性有毒物质相关的鲁棒性的反应？拟议的研究的目标是阐明皮质醇在鱼类对有毒物质的生理反应中的作用，并检验皮质醇在急性潜在致命有毒物质暴露下具有有益作用的假设，但在亚致死慢性暴露下是有害的，会产生显著的代谢成本。皮质醇应激反应的模式和对毒物的脆弱性之间的关系将进行研究，比较，多物种的方法整合毒理学和应激生理学，与整个动物实验室和现场曝光，药理学操作的皮质醇状态和原代细胞培养。皮质醇反应的模式，从多个测量中获得的个体鱼使用遏制水皮质醇，将其特征在于在四个孵化场繁殖的鱼类（青少年虹鳟鱼，溪鳟，黑头呆鱼，金鱼），显示不同的脆弱性测试毒物（亚硒酸盐，镉，农药农达）。接下来，皮质醇状态将被操纵，以通过甲吡酮和RU 486阻断皮质醇分泌和皮质醇受体，或用合成皮质醇升高皮质醇。然后，在实验室或在暴露于市政污水的地点的笼子里，将皮质醇处理的鱼急性或慢性暴露于有毒物质。 生存，生长，代谢和生殖状态，氧化应激，和特定的基因，包括热休克蛋白70，星星和HSD的表达，将在鱼能够安装正常的压力反应和皮质醇操纵的鱼进行比较，以测试的假设，一个强大的，但短暂的皮质醇应激反应，使鱼更有效地处理有毒物质比长期的反应或没有反应。在体外，虹鳟鱼头肾细胞和受精卵将暴露于测试毒物，在培养物中有或没有皮质醇。将测量细胞活力、氧化应激、胚胎发育和基因表达，以提供毒理学数据，并检验皮质醇在特定浓度和暴露时间下具有保护作用的假设。这项研究将为皮质醇在对毒物的生理反应中的作用以及介导物种敏感性差异的机制提供新的认识。

The physiological stress response is elicited when organisms are exposed to potentially harmful stimuli. Cortisol is a key hormonal effector of the response at tissue level in fish. The stress response has been characterized for many species and diverse stressors, including toxicants, yet key fundamental questions remain: is the stress response beneficial or detrimental to the organism during exposure to toxicants; is vulnerability to toxicants related to robustness of the response? The goal of the proposed research is to elucidate the role of cortisol in the physiological response to toxicants in fish and test the hypothesis that cortisol has beneficial effects under acute potentially lethal toxicant exposures, but is detrimental, engendering significant metabolic costs, under sublethal chronic exposures. The relationship between the pattern of the cortisol stress response and vulnerability to toxicants will be investigated with a comparative, multispecies approach integrating toxicology and stress physiology, with whole animal laboratory and field exposures, pharmacological manipulations of the cortisol status and primary cell cultures. The patterns of the cortisol response, obtained from multiple measurements in individual fish using containment water cortisol, will be characterized in four hatchery-bred fish species (juvenile rainbow trout, brook trout, fathead minnow, goldfish) which display differences in vulnerability to test toxicants (selenite, cadmium, pesticide Roundup). Next, the cortisol status will be manipulated pharmacologically to either block cortisol secretion and cortisol receptors by metyrapone and RU 486, or elevate cortisol with synthetic cortisol. Cortisol-manipulated fish will then be exposed to toxicants acutely or chronically in the laboratory, or in cages at sites exposed to municipal effluents.  Survival, growth, metabolic and reproductive status, oxidative stress, and expression of specific genes including hsp 70, StAR, and HSD, will be compared in fish able to mount the normal stress response and in cortisol-manipulated fish, to test the hypothesis that a robust but brief cortisol stress response enables the fish to deal with toxicants more efficiently than a prolonged response or no response. In vitro, rainbow trout head kidney cells and fertilized eggs will be exposed to the test toxicants, with or without cortisol in the culture. Cell viability, oxidative stress, embryonic development and gene expression will be measured to provide toxicological data and test the hypothesis that cortisol, at specific concentrations and timing of the exposure, has protective effects. The proposed research will provide new understanding of the role of cortisol in the physiological response to toxicants and the mechanisms mediating species differences in sensitivity.**