Ando Hironori, Swanson Penny, Kitani Tomoko, Koide Nobuhisa, Okada Houji, Ueda Hiroshi, Urano Akihisa
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan.
Gen Comp Endocrinol. 2004 May 15;137(1):109-21. doi: 10.1016/j.ygcen.2004.02.012.
Effects of salmon gonadotropin-releasing hormone (sGnRH) and estradiol-17beta (E2) on gene expression and release of gonadotropins (GTHs) were examined in masu salmon (Oncorhynchus masou) using primary pituitary cell cultures at three reproductive stages, initiation of sexual maturation in May, pre-spawning in July, and spawning in September. Amounts of GTH subunit mRNAs were determined by real-time polymerase chain reaction, and levels of GTH released in the medium were determined by RIA. In control cells, the amounts of three GTH subunit mRNAs (alpha2, FSHbeta, and LHbeta) peaked in July prior to spawning. FSH release spontaneously increased with gonadal maturation and peaked in September, whereas LH release remained low until July and extensively increased in September. Addition of E2 to the culture extensively increased the amounts of LHbeta mRNA in May and July in both sexes. It also increased the alpha2 mRNA in July in the females. In contrast, sGnRH alone did not have any significant effects on the amounts of three GTH subunit mRNAs at all stages, except for the elevation of alpha2 and FSHbeta mRNAs in July in the females. Nevertheless, synergistic effects by sGnRH and E2 were evident for all three GTH subunit mRNAs. In May, sGnRH in combination with E2 synergistically increased the amounts of LHbeta mRNA in the males and alpha2 mRNA in the females. However, in July the combination suppressed the amounts of alpha2 and FSHbeta mRNAs in the females. sGnRH alone stimulated LH release at all stages in both sexes, and the release was synergistically enhanced by E2. Synergistic stimulation of FSH release was also observed in May and July in both sexes. These results indicate that a functional interaction of sGnRH with E2 is differently involved in synthesis and release of GTH. The synergistic interaction modulates GTH synthesis differentially, depending on subunit, stage, and gender, whereas it potentiates the activity of GnRH to release GTH in any situation.
利用原代垂体细胞培养技术，在三个生殖阶段（5月性成熟开始、7月产卵前以及9月产卵时）对马苏大麻哈鱼（Oncorhynchus masou）进行研究，以检测鲑鱼促性腺激素释放激素（sGnRH）和17β-雌二醇（E2）对促性腺激素（GTHs）基因表达和释放的影响。通过实时聚合酶链反应测定GTH亚基mRNA的量，并用放射免疫分析法测定培养基中释放的GTH水平。在对照细胞中，三种GTH亚基mRNA（α2、FSHβ和LHβ）的量在7月产卵前达到峰值。随着性腺成熟，FSH释放量自发增加，并在9月达到峰值，而LH释放在7月之前一直较低，在9月大幅增加。在5月和7月，向培养物中添加E2可显著增加两性LHβ mRNA的量。在7月，它还增加了雌性α2 mRNA的量。相比之下，单独的sGnRH在所有阶段对三种GTH亚基mRNA的量均无显著影响，但在7月可使雌性α2和FSHβ mRNA升高。然而，sGnRH和E2对所有三种GTH亚基mRNA均有明显的协同作用。5月，sGnRH与E2联合使用可协同增加雄性LHβ mRNA和雌性α2 mRNA的量。然而，在7月，该组合抑制了雌性α2和FSHβ mRNA的量。单独的sGnRH在所有阶段均可刺激两性LH释放，E2可协同增强这种释放。在5月和7月，两性中还观察到对FSH释放的协同刺激作用。这些结果表明，sGnRH与E2的功能相互作用在GTH的合成和释放中发挥不同作用。这种协同相互作用根据亚基、阶段和性别差异调节GTH合成，而在任何情况下都能增强GnRH释放GTH的活性。
