Senthilkumaran B, Okuzawa K, Gen K, Ookura T, Kagawa H
Inland Station, National Research Institute of Aquaculture, Tamaki, Japan.
J Neuroendocrinol. 1999 Mar;11(3):181-6. doi: 10.1046/j.1365-2826.1999.00304.x.
Specific and sensitive radioimmunoassays (RIAs) were newly developed for two types of gonadotropin-releasing hormone (GnRH), namely, seabream (sb) GnRH and chicken (c) GnRH-II. We employed these two RIAs together with a previously reported RIA for salmon (s) GnRH to study the presence and regional distribution of these three GnRHs in the brains and pituitaries of four perciform fishes (red seabream, Pagrus major; black seabream, Acanthopagrus schlegeli; striped knifejaw, Oplegnathus fasciatus; and Nile tilapia, Oreochromis niloticus), as well as clarify seasonal changes in levels of these GnRHs in the brain and pituitary of red seabream. All three GnRHs were found in brains of all fishes examined, with regional distributions in the brains of the three GnRHs being rather similar. sbGnRH was abundant in telencephalon and hypothalamus. cGnRH-II was concentrated from the middle to posterior part of the brain and distributed throughout the brain. sGnRH was concentrated in the olfactory bulb and distributed all over the brain, as was cGnRH-II. The dominant form of GnRH in the pituitary was sbGnRH, with levels 500- to 2400-fold higher than those of sGnRH, while cGnRH-II was undetectable in all four species. In the brain and pituitary of female red seabream, levels of both brain and pituitary sbGnRH increased from October (immature phase) and reached a peak in April (spawning phase), reflecting the increase in gonadosomatic index and vitellogenesis. However, levels of sbGnRH remained high only in the pituitary of completely regressed fish in June. Levels of both sGnRH and cGnRH-II in the brain were higher in the regressed phase and remained lower during the spawning phase. From these and previous results, it appears that sbGnRH is physiologically the most important form of GnRH in reproduction in red seabream and, probably, in other perciforms also.
针对两种促性腺激素释放激素（GnRH），即鲷鱼（sb）GnRH和鸡（c）GnRH-II，新开发了特异性和敏感性均高的放射免疫分析方法（RIA）。我们将这两种RIA与先前报道的用于鲑鱼（s）GnRH的RIA一起使用，来研究这三种GnRH在四种鲈形目鱼类（真鲷，Pagrus major；黑鲷，Acanthopagrus schlegeli；条石鲷，Oplegnathus fasciatus；尼罗罗非鱼，Oreochromis niloticus）的脑和垂体中的存在情况及区域分布，同时阐明真鲷脑和垂体中这些GnRH水平的季节性变化。在所检测的所有鱼类的脑中均发现了这三种GnRH，三种GnRH在脑中的区域分布相当相似。sbGnRH在端脑和下丘脑含量丰富。cGnRH-II集中在脑的中部到后部，并分布于整个大脑。sGnRH集中在嗅球，并像cGnRH-II一样分布于整个大脑。垂体中GnRH的主要形式是sbGnRH，其水平比sGnRH高500至2400倍，而在所有四个物种中均未检测到cGnRH-II。在雌性真鲷的脑和垂体中，脑和垂体中的sbGnRH水平从10月（未成熟阶段）开始升高，并在4月（产卵阶段）达到峰值，这反映了性腺指数和卵黄发生的增加。然而，仅在6月完全退化的鱼的垂体中，sbGnRH水平仍保持较高。脑中sGnRH和cGnRH-II的水平在退化阶段较高，而在产卵阶段较低。从这些结果和之前的结果来看，似乎sbGnRH在生理上是真鲷繁殖中最重要的GnRH形式，可能在其他鲈形目鱼类中也是如此。
