Jodo Aya, Kitahashi Takashi, Taniyama Shinya, Ueda Hiroshi, Urano Akihisa, Ando Hironori
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
Gen Comp Endocrinol. 2005 Oct;144(1):1-9. doi: 10.1016/j.ygcen.2005.04.001.
Five types of gonadotropin-releasing hormone receptor (GnRH-R) genes, designated as msGnRH-R1, R2, R3, R4, and R5, are expressed in the brain and pituitary of masu salmon (Oncorhynchus masou). In the present study, seasonal changes in the expression of these five genes were examined in the pituitary to elucidate their roles in GnRH action during growth and sexual maturation. In addition, the seasonal variation of these genes in response to GnRH was examined in a GnRH analog (GnRHa) implantation experiment. Pituitary samples were collected 1 week after the implantation every month from immaturity through spawning. The absolute amount of GnRH-R mRNA in single pituitaries was determined by real-time PCR assays. Among the five genes, R4 was predominantly expressed in the pituitaries. In the immature fish, the amount of GnRH-R mRNA varied with seasons and subtypes. In the pre-spawning period, R1 and R4 mRNAs in both sexes and R2 and R3 mRNAs in the females increased 4- to 20-fold and then decreased in the spawning season. The effects of GnRHa treatment were significantly different in both sexes. In the females, GnRHa tended to elevate the expression of all the subtypes of GnRH-R genes in various stages during the experimental period, whereas it had almost no apparent effects in the males. These results indicate that the expression of the five GnRH-R genes is seasonally variable and may be related to the responses of the pituitary hormone genes to GnRH, and the regulation of GnRH-R genes by GnRH is different in both sexes.
在马苏大麻哈鱼（Oncorhynchus masou）的大脑和垂体中表达有五种促性腺激素释放激素受体（GnRH-R）基因，分别命名为msGnRH-R1、R2、R3、R4和R5。在本研究中，检测了这五种基因在垂体中的表达季节性变化，以阐明它们在生长和性成熟过程中GnRH作用中的角色。此外，在一项GnRH类似物（GnRHa）植入实验中检测了这些基因对GnRH的季节性变化反应。从未成熟到产卵，每月在植入后1周采集垂体样本。通过实时PCR测定法确定单个垂体中GnRH-R mRNA的绝对量。在这五个基因中，R4在垂体中主要表达。在未成熟鱼中，GnRH-R mRNA的量随季节和亚型而变化。在产卵前期，两性中的R1和R4 mRNA以及雌性中的R2和R3 mRNA增加4至20倍，然后在产卵季节下降。GnRHa处理的效果在两性中显著不同。在雌性中，GnRHa在实验期间倾向于提高各个阶段所有GnRH-R基因亚型的表达，而在雄性中几乎没有明显影响。这些结果表明，五种GnRH-R基因的表达具有季节性变化，可能与垂体激素基因对GnRH的反应有关，并且GnRH对GnRH-R基因的调控在两性中有所不同。
