Yuan Mingzhe, Jia Qianqian, Wang Ting, Lu Qi, Tang Langlang, Wang Youji, Lu Weiqun
National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai 201306, China; The Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, Shanghai 201306, China.
National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai 201306, China.
Gen Comp Endocrinol. 2017 Dec 1;254:8-13. doi: 10.1016/j.ygcen.2017.09.005. Epub 2017 Sep 18.
Prolactin (PRL) and growth hormone (GH) play important roles in regulating salt and water balance through osmoregulatory organs in vertebrates. The aim of this study was to investigate the dynamic changes of GH/PRL hormone gene expressions in the pituitary gland and their receptors in gill and kidney, as well as the plasma osmolality when the olive flounder fish Paralichthys olivaceus were acclimated in freshwater (FW) conditions. After transfer from seawater (SW) to freshwater (FW), the osmolality of FW-adaption fish reached the lowest level at 1d which rose slightly afterwards. However, the hormone gene expression of PRL increased from 2d, reaching its peak at 5d, and then decreased at 14d. At this time, the value was still significantly higher than the control, showing a similar trend to the plasma hormone PRL. In contrast, the pituitary mRNA level of GH significantly decreased at 1d and then returned to normal levels. The mRNA levels of PRL receptor (PRLR) in both gill and kidney displayed a similar trend to the pituitary PRL. We also observed the synchronous expression trend of the renal PRLR with pituitary PRL (5d) and the asynchronous expression peaks between branchial (8d) and renal PRLR (5d). Significant responses of GH and its receptor (GHR) in both gill and kidney during the FW-acclimation were not observed. Nevertheless, the gene expression of GH receptor variant (GHR-V) in both gill and kidney declined at 2d, indicating unknown osmoregulatory functions of GHR-V. Collectively, our results provided more insights of the PRL, GH and their corresponding receptors in modulating osmoregulatory responses, representing an important aspect of FW-acclimation in flounder fish.
催乳素（PRL）和生长激素（GH）在脊椎动物中通过渗透调节器官调节盐和水平衡方面发挥着重要作用。本研究的目的是调查牙鲆（Paralichthys olivaceus）在淡水（FW）条件下适应过程中，垂体中GH/PRL激素基因表达及其鳃和肾中受体的动态变化，以及血浆渗透压的变化。从海水（SW）转移到淡水（FW）后，适应FW的鱼的渗透压在第1天达到最低水平，随后略有上升。然而，PRL的激素基因表达从第2天开始增加，在第5天达到峰值，然后在第14天下降。此时，该值仍显著高于对照组，与血浆激素PRL呈现相似趋势。相比之下，垂体中GH的mRNA水平在第1天显著下降，然后恢复到正常水平。鳃和肾中PRL受体（PRLR）的mRNA水平与垂体PRL呈现相似趋势。我们还观察到肾PRLR与垂体PRL（第5天）的同步表达趋势，以及鳃（第8天）和肾PRLR（第5天）之间的异步表达峰值。在FW适应过程中，未观察到鳃和肾中GH及其受体（GHR）的显著反应。然而，鳃和肾中GH受体变体（GHR-V）的基因表达在第2天下降，表明GHR-V具有未知的渗透调节功能。总体而言，我们的结果为PRL、GH及其相应受体在调节渗透调节反应方面提供了更多见解，这是牙鲆FW适应的一个重要方面。
