Department of Biological Sciences, University of Idaho, Moscow, ID 83844, USA.
Gen Comp Endocrinol. 2012 Sep 15;178(3):556-61. doi: 10.1016/j.ygcen.2012.06.010. Epub 2012 Jun 22.
Estrogens are critical hormones involved in reproduction and need to bind to estrogen receptors in target organs for biological activity. Fishes have two distinct estrogen receptor subtypes, alpha (α) and beta (β), with variable combinations of additional isoforms of each subtype dependent on the history of genome duplication within a taxon. The comparative expression patterns of estrogen receptor isoforms during the female reproductive cycle will provide important insights into the unique function and importance of each. The purpose of this study was to measure the mRNAs for the four estrogen receptor isoforms (erα1, erα2, erβ1, erβ2) in the liver and ovary of adult, female rainbow trout over the course of an annual reproductive cycle. The expression of estrogen receptor mRNA isoforms was measured by quantitative real-time RT-PCR. Several reproductive indices (gonadosomatic index, maximum oocyte diameter, plasma estradiol-17β, plasma vitellogenin, and ovulation) were also quantified for comparison and used in a correlation analysis to examine any inter-relationships. Of the four isoforms, the expression of erα1 was highest in the liver, and had a significant positive correlation with liver erβ1 expression. Liver expression of erα2 mRNA was the lowest, but showed a significant positive correlation with maximum oocyte diameter in the ovary. The pattern of the erβ isoforms in liver was one of initially elevated mRNA expression followed by a gradual decrease as reproductive development proceeded. In the ovary the erβ1 isoform had the highest mRNA expression of all estrogen receptor isoforms, at the beginning of the reproductive cycle, but then decreased afterward. Both ovarian erβ isoforms had a significant positive correlation with one another. In contrast, erα2 mRNA expression showed a high maximum level in the ovary near the end of the cycle along with a significant positive correlation with plasma estradiol-17β levels; the highest gonadosomatic indices, maximum oocyte diameter, and vitellogenin levels occurred then too.
雌激素是参与生殖的关键激素，需要与靶器官中的雌激素受体结合才能发挥生物活性。鱼类有两种不同的雌激素受体亚型，即α（α）和β（β），每种亚型的额外同工型的组合取决于在一个分类群内的基因组复制历史。在雌性生殖周期中，雌激素受体同工型的比较表达模式将为每个同工型的独特功能和重要性提供重要的见解。本研究的目的是测量成年雌性虹鳟鱼肝脏和卵巢中四种雌激素受体同工型（erα1、erα2、erβ1、erβ2）在年度生殖周期过程中的 mRNA。通过定量实时 RT-PCR 测量雌激素受体 mRNA 同工型的表达。还量化了几个生殖指数（性腺指数、最大卵径、血浆雌二醇-17β、血浆卵黄蛋白原和排卵）进行比较，并用于相关分析，以检查任何相互关系。在这四种同工型中，erα1 在肝脏中的表达最高，与肝脏 erβ1 的表达呈显著正相关。肝 erα2 mRNA 的表达最低，但与卵巢中最大卵径呈显著正相关。肝中 erβ 同工型的表达模式为先升高 mRNA 表达，然后随着生殖发育的进行逐渐降低。在卵巢中，erβ1 同工型在生殖周期开始时具有所有雌激素受体同工型中最高的 mRNA 表达，但随后降低。两种卵巢 erβ 同工型彼此之间呈显著正相关。相比之下，erα2 mRNA 表达在接近周期结束时在卵巢中达到最高水平，并与血浆雌二醇-17β水平呈显著正相关；性腺指数、最大卵径和卵黄蛋白原水平也达到最高。
