Effects of pollutants on interrenal steroidogenesis:mechanisms underlying species differences in vulnerability

对应激刺激的识别和反应是一种生理反应，发生在所有脊椎动物中，包括硬骨鱼。皮质醇的分泌在急性暴露于包括污染物在内的应激源时被激活，血液皮质醇的增加被认为是有益的。然而，过度激活应激反应可能是有害的，而且有新的证据表明，肾间组织本身可能是污染物的目标。因此，皮质醇在硬骨鱼对污染物的生理反应中的作用尚不完全清楚。我们的研究项目主要集中在肾间类固醇的生成，即在硬骨鱼的肾间组织中发现的类固醇生成细胞与其他类型的细胞一起合成皮质醇。拟议的研究计划的目的是确定皮质醇应激反应和类固醇生成细胞对污染物的脆弱性的不同物种的细胞特征和机制。对于虹鱼(对污染物高度敏感)和黑头鱼(对污染物不太敏感)，我们将使用体外方法，通过Percoll梯度纯化整个肾间组织或类固醇生成细胞，并结合整个鱼类的体内暴露。将在体外和体内评估测试污染物(Cd-非必需金属；Se-必需金属；农达-农药)对类固醇生成细胞功能完整性(基础和ACTH刺激的皮质醇和cAMP产生、细胞活力)、其氧化状态(过氧化氢酶、GSH/GSSG、SOD)和细胞内钙稳态的影响。皮质醇在体内暴露于毒物中的作用将使用甲替拉酮和皮质醇受体阻滞剂RU-486进行研究。还将评估温度对毒物反应的影响，鉴于气候变化和我们的水生生态系统逐渐变暖，这是一个重要的问题。彩虹鲑鱼和小鱼的比较将提供数据，帮助我们了解使生物体及其组织容易受到污染物影响的细胞特征。这些知识可用于制定水质准则，以保护我们的水生物种和管理我们的渔业。

Recognition and reaction to stressful stimuli is a physiological response that occurs in all vertebrates, including teleost fish. Secretion of cortisol is activated during acute exposures to stressors, including pollutants, and the increase in blood cortisol is believed to be beneficial. However overactivation of the stress response can be detrimental and there is new evidence that the interrenal tissue itself can be a target of pollutants. Thus the role of cortisol in the physiological response to pollutants in teleosts is not entirely clear.   Our research program is focused on interrenal steroidogenesis, synthesis of cortisol by steroidogenic cells found, with other cell types, in the interrenal tissue of teleosts. The objective of the proposed research program is to determine the cellular characteristics and the mechanisms underlying species-specific differences in the cortisol stress response and in vulnerability of the steroidogenic cells to pollutants. Working with rainbow trout (highly sensitive to pollutants) and fathead minnow (less sensitive), we will use an in vitro approach, with either the whole interrenal tissue or steroidogenic cells purified with Percoll gradients, in combination with in vivo exposures of whole fish. The effects of test pollutants (Cd-non essential metal; Se-essential metal; Roundup-pesticide) on the functional integrity of the steroidogenic cells (basal and ACTH-stimulated cortisol and cAMP production, cell viability), their oxidative status  (catalase, GSH/GSSG, SOD) and intracellular calcium homeostasis will be assessed in vitro and in vivo in the two fish species. The role of cortisol during in vivo exposures to the toxicants will be investigated using metyrapone and RU-486, a blocker of cortisol receptors. Effects of temperature on the responses to the toxicants will be also assessed, an issue of importance given climate change and the gradual warming of our aquatic ecosystems. Comparison of rainbow trout and the minnow will provide data to help us understand the cellular characteristics that make organisms and their tissues vulnerable to pollutants. This knowledge can be used in setting up of water quality guidelines that will protect our aquatic species and in management of our fisheries.