Aruna Adimoolam, Nagarajan Ganesan, Chang Ching-Fong
Department of Aquaculture, National Taiwan Ocean University, Keelung 20224, Taiwan.
Department of Aquaculture, National Taiwan Ocean University, Keelung 20224, Taiwan; The Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung 20224, Taiwan.
Gen Comp Endocrinol. 2015 Jan 15;211:154-64. doi: 10.1016/j.ygcen.2014.12.005. Epub 2014 Dec 20.
To analyze and compare the stress and osmoregulatory hormones and receptors in pituitary during acute salinity changes, the expression patterns of corticotropin releasing hormone (crh) in hypothalamus, prolactin (prl) releasing peptide (pRrp) in telencephalon and diencephalon, glucocorticoid receptors 2 (gr2), and mineralocorticoid receptor (mr), crh-r, pro-opiomelanocorticotropin (pomc), pRrp, prl, dopamine 2 receptor (d2-r), growth hormone (gh), gh-receptor (gh-r) and insulin-like growth hormone (igf-1) transcripts in pituitary were characterized in euryhaline tilapia. The results indicate that the crh transcripts increased in the hypothalamus and rostral pars distalis of the pituitary after the transfer of fish to SW. Similarly, the pRrp transcripts were more abundant in SW acclimated tilapia forebrain and hypothalamus. The crh-r, gr2 and mr transcripts were more expressed in rostral pars distalis and pars intermedia of pituitary at SW than FW tilapia. The data indicate that the SW acclimation stimulates these transcripts in the specific regions of the brain and pituitary which may be related to the activation of the hypothalamic-pituitary-interrenal (HPI)-axis. The results of dual in situ hybridization reveal that the transcripts of crh-r, gr2 and mr with pomc are highly co-localized in corticotrophs of pituitary. Furthermore, we demonstrate high expression of pRrp in the brain and low expression of pRrp and prl transcripts in the pituitary of SW fish. No crh-r and corticosteroid receptors were co-localized with prl transcripts in the pituitary. The gh-r and igf-1 mRNA levels were significantly increased in SW acclimated tilapia pituitary whereas there was no difference in the gh mRNA levels. The data suggest that the locally produced pRrp and d2-r may control and regulate the expression of prl mRNA in pituitary. Therefore, the dual roles of pRrp are involved in the stress (via brain-pituitary) and osmoregulatory (via pituitary) pathways in tilapia exposed to acute salinity changes.
为了分析和比较急性盐度变化期间垂体中的应激和渗透压调节激素及受体，研究了广盐性罗非鱼下丘脑促肾上腺皮质激素释放激素（crh）、端脑和间脑中催乳素（prl）释放肽（pRrp）、糖皮质激素受体2（gr2）、盐皮质激素受体（mr）、crh-r、阿黑皮素原（pomc）、pRrp、prl、多巴胺2受体（d2-r）、生长激素（gh）、gh受体（gh-r）和胰岛素样生长激素（igf-1）转录本在垂体中的表达模式。结果表明，将鱼转移到海水后，下丘脑和垂体远侧部前部的crh转录本增加。同样，在适应海水的罗非鱼前脑和下丘脑中，pRrp转录本更为丰富。与淡水罗非鱼相比，海水适应的罗非鱼垂体远侧部前部和中间部的crh-r、gr2和mr转录本表达更多。数据表明，海水适应刺激了大脑和垂体特定区域的这些转录本，这可能与下丘脑-垂体-肾间（HPI）轴的激活有关。双重原位杂交结果显示，crh-r、gr2和mr与pomc的转录本在垂体促肾上腺皮质细胞中高度共定位。此外，我们证明了pRrp在脑中高表达，而在海水鱼垂体中pRrp和prl转录本低表达。垂体中没有crh-r和皮质类固醇受体与prl转录本共定位。适应海水的罗非鱼垂体中gh-r和igf-1 mRNA水平显著升高，而gh mRNA水平没有差异。数据表明，局部产生 的pRrp和d2-r可能控制和调节垂体中prl mRNA的表达。因此，pRrp的双重作用参与了暴露于急性盐度变化的罗非鱼的应激（通过脑-垂体）和渗透压调节（通过垂体）途径。
