Onuma Takeshi A, Ando Hironori, Koide Nobuhisa, Okada Houji, Urano Akihisa
Department of Animal and Marine Bioresource Science, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka 812-8581, Japan.
Gen Comp Endocrinol. 2007 May 15;152(1):64-72. doi: 10.1016/j.ygcen.2007.02.024. Epub 2007 Mar 2.
Expression of genes encoding gonadotropin (GTH) subunits in the salmon pituitary was regulated by salmon gonadotropin-releasing hormone (sGnRH) and sex steroid hormones in a reproductive stage-dependent manner, probably through DNA-binding transcription factors. Direct effects of these hormones on expression of genes encoding salmon fushi tarazu factor 1 homolog (sFF1-I) and estrogen receptor alpha (ERalpha) were therefore examined by use of primary pituitary cell cultures of masu salmon at different reproductive stages. Pituitaries were collected in March (before initiation of gonadal maturation), in May (early maturing), in July (late maturing), and in September (spawning period). Amounts of sFF1-I and ERalpha mRNAs in the pituitary cells were determined by real-time polymerase chain reactions after a treatment with sGnRH, estradiol-17beta (E2), testosterone (T) or 11-ketotestosterone (11KT). The amounts of sFF1-I mRNA were elevated by E2 in the males, and by sGnRH and T in the females before initiation of gonadal maturation and at the early maturing stage. The amounts of ERalpha mRNA in the early maturing females were elevated by sGnRH. Effects of sGnRH were not significant at the late maturing and spawning stages. The amounts of ERalpha mRNA in the spawning males were halved by 11KT and E2, and those of sFF1-I and ERalpha mRNAs in the late maturing females were decreased by T and 11KT. These results indicated that responsiveness of sFF1-I and ERalpha genes to sGnRH and sex steroid hormones is seasonally variable in relation to reproductive stages. Expression of sFF1 and ERalpha genes should be stimulated at the early stages of gonadal maturation prior to increases in the amounts of GTH subunit mRNAs, while attenuated after the late maturing period when stored amounts of GTH subunit mRNAs reached near the maximum.
鲑鱼垂体中促性腺激素（GTH）亚基编码基因的表达受鲑鱼促性腺激素释放激素（sGnRH）和性类固醇激素以生殖阶段依赖性方式调控，可能是通过DNA结合转录因子实现的。因此，利用不同生殖阶段的马苏鲑原代垂体细胞培养物，研究了这些激素对鲑鱼腹侧无翅型基因1同源物（sFF1-I）和雌激素受体α（ERα）编码基因表达的直接影响。垂体分别于3月（性腺成熟开始前）、5月（早熟期）、7月（晚熟期）和9月（产卵期）采集。在用sGnRH、雌二醇-17β（E2）、睾酮（T）或11-酮睾酮（11KT）处理后，通过实时聚合酶链反应测定垂体细胞中sFF1-I和ERα mRNA的量。在性腺成熟开始前和早熟期，雄性中sFF1-I mRNA的量因E2而升高，雌性中则因sGnRH和T而升高。早熟雌性中ERα mRNA的量因sGnRH而升高。在晚熟期和产卵期，sGnRH的作用不显著。产卵雄性中ERα mRNA的量因11KT和E2而减半，晚熟雌性中sFF1-I和ERα mRNA的量因T和11KT而减少。这些结果表明，sFF1-I和ERα基因对sGnRH和性类固醇激素的反应性随生殖阶段而季节性变化。在GTH亚基mRNA量增加之前的性腺成熟早期，sFF1和ERα基因的表达应受到刺激，而在晚熟期之后，当GTH亚基mRNA的储存量接近最大值时，表达则会减弱。
