Onuma Takeshi, Ando Hironori, Koide Nobuhisa, Okada Houji, Urano Akihisa
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan.
Gen Comp Endocrinol. 2005 Sep 1;143(2):129-41. doi: 10.1016/j.ygcen.2005.03.003. Epub 2005 Apr 9.
Expression of genes encoding growth hormone (GH), prolactin (PRL), and somatolactin (SL) in growing and maturing salmon was stimulated by gonadotropin-releasing hormone (GnRH) analog during particular periods of the life cycle. GnRH therefore appears to directly and/or indirectly regulate gene expression for GH, PRL, and SL in combination with the pituitary-gonadal axis, such as sex steroid hormones. Direct effects of salmon GnRH (sGnRH), estradiol-17beta (E2), testosterone, and 11-ketotestosterone (11KT) on the amounts of GH, PRL, and SL mRNAs were thus examined using primary pituitary cell cultures of masu salmon at the four reproductive stages. We also determined the amounts of mRNA encoding pituitary specific POU homeodomain transcription factor (Pit-1) by real-time polymerase chain reactions. The amounts of GH, PRL, and SL mRNAs in the control cells elevated with gonadal maturation, coincidently with those of Pit-1 mRNA. sGnRH at 1.0 nM elevated the amounts of all mRNAs examined in the pre-spawning females, whereas significant effects were not observed with 100 nM sGnRH at any reproductive stages. Sex steroid hormones had no significant effects before initiation of gonadal maturation and at the maturing stage. In the males, E2 tended to decrease the amounts of SL mRNA in the pre-spawning stage. In the females, E2 and 11KT increased the amounts of PRL and SL mRNAs in the pre-spawning stage, but halved those of PRL mRNA in the spawning stage. The amounts of Pit-1 mRNA changed coincidently with those of PRL and SL mRNAs at all examined stages. The effects of E2 alone were abolished by 100 nM sGnRH. The present results indicated that both sGnRH and steroid hormones directly modulate synthesis of Pit-1, and further expression of PRL and SL genes. sGnRH may indirectly regulate GH/PRL/SL family hormone genes through the pituitary-gonadal axis, particularly in the late stage of gametogenesis.
在鲑鱼生长和成熟的特定生命周期阶段，促性腺激素释放激素（GnRH）类似物可刺激生长激素（GH）、催乳素（PRL）和生长抑素（SL）编码基因的表达。因此，GnRH似乎与垂体 - 性腺轴（如性类固醇激素）一起直接和/或间接调节GH、PRL和SL的基因表达。本研究使用处于四个生殖阶段的马苏大麻哈鱼的原代垂体细胞培养物，检测了鲑鱼GnRH（sGnRH）、雌二醇 - 17β（E2）、睾酮和11 - 酮睾酮（11KT）对GH、PRL和SL mRNA含量的直接影响。我们还通过实时聚合酶链反应测定了垂体特异性POU同源结构域转录因子（Pit - 1）编码mRNA的含量。对照细胞中GH、PRL和SL mRNA的含量随着性腺成熟而升高，与Pit - 1 mRNA的变化一致。1.0 nM的sGnRH可提高产卵前雌性中所有检测mRNA的含量，而在任何生殖阶段，100 nM的sGnRH均未观察到显著影响。性类固醇激素在性腺成熟开始前和成熟阶段没有显著影响。在雄性中，E2在产卵前阶段倾向于降低SL mRNA的含量。在雌性中，E2和11KT在产卵前阶段增加了PRL和SL mRNA的含量，但在产卵阶段使PRL mRNA的含量减半。在所有检测阶段，Pit - 1 mRNA的含量与PRL和SL mRNA的含量变化一致。100 nM的sGnRH可消除单独E2的作用。目前的结果表明，sGnRH和类固醇激素均可直接调节Pit - 1的合成，进而调节PRL和SL基因的进一步表达。sGnRH可能通过垂体 - 性腺轴间接调节GH/PRL/SL家族激素基因，特别是在配子发生后期。
