Department of Biological Sciences (T.K., M.A., C.K., H.A., S.K., Y.O.), Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan; and Laboratory of Fish Biology (H.A.), Graduate School of Bioagricultural Sciences, Nagoya University, Aichi 464-8601, Japan.
Endocrinology. 2014 Feb;155(2):536-47. doi: 10.1210/en.2013-1642. Epub 2013 Nov 18.
Two types of gonadotropins, luteinizing hormone (LH) and follicle stimulating hormone (FSH), are important pituitary hormones for sexual maturation and reproduction, and both of them are centrally regulated by gonadotropin-releasing hormone (GnRH) from the hypothalamus. In mammals, these two gonadotropins are secreted from a single type of gonadotrope. The mechanisms of differential regulation by GnRH of the release of two types of gonadotropins with different secretory profiles are still unknown. In teleosts, however, LH and FSH are secreted from separate cellular populations, unlike in mammals. This feature makes them useful for studying the regulatory mechanisms of LH and FSH secretions independently. Here, we generated transgenic medaka lines that express Ca(2+) indicator protein, inverse-pericam, specifically in the LH or FSH cells. We performed cell-type-specific Ca(2+) imaging of LH and FSH cells, respectively, using the whole brain-pituitary preparations of these transgenic fish in which all neural circuits and GnRH neuronal projection to the pituitary are kept intact. LH and FSH cells showed different Ca(2+) responses to GnRH. The results suggest differential regulation mechanisms for LH and FSH release by GnRH. Moreover, we also succeeded in detecting the effect on LH cells of endogenous GnRH peptide, which was released by electrical stimulation of the axons of GnRH1 neurons. Thus, our newly developed experimental model system using the whole brain-pituitary in vitro preparation of the transgenic medaka is a powerful tool for analyzing the differential regulatory mechanisms of the release of LH and FSH by multisynaptic neural inputs to the pituitary.
两种促性腺激素，黄体生成素（LH）和卵泡刺激素（FSH），对于性成熟和生殖至关重要，它们都是由下丘脑的促性腺激素释放激素（GnRH）中枢调控的。在哺乳动物中，这两种促性腺激素都是由一种促性腺细胞分泌的。GnRH 对具有不同分泌特征的两种促性腺激素释放的差异调节机制尚不清楚。然而，在鱼类中，LH 和 FSH 是由不同的细胞群分泌的，与哺乳动物不同。这一特征使它们成为研究 LH 和 FSH 分泌的独立调节机制的有用工具。在这里，我们生成了转基因斑马鱼系，其特异性地在 LH 或 FSH 细胞中表达 Ca（2+）指示剂蛋白 inverse-pericam。我们使用这些转基因鱼的全脑垂体制备物，分别对 LH 和 FSH 细胞进行细胞类型特异性 Ca（2+）成像，其中所有神经回路和 GnRH 神经元投射到垂体都保持完整。LH 和 FSH 细胞对 GnRH 表现出不同的 Ca（2+）反应。结果表明 GnRH 对 LH 和 FSH 释放的调节机制不同。此外，我们还成功地检测到内源性 GnRH 肽对 LH 细胞的影响，该肽是通过 GnRH1 神经元轴突的电刺激释放的。因此，我们使用转基因斑马鱼的全脑垂体体外制备物开发的新实验模型系统是分析多突触神经输入对垂体释放 LH 和 FSH 的差异调节机制的有力工具。
