Department of Animal Physiology and Endocrinology, University of Agriculture in Krakow, Al. Mickiewicza 24/28, 30-059 Krakow, Poland.
Gen Comp Endocrinol. 2013 Sep 1;190:68-75. doi: 10.1016/j.ygcen.2013.04.012. Epub 2013 Apr 28.
In all vertebrates, including birds, the normal development of the ovary and ovarian follicles is under the regulatory influence of hormones produced by the reproductive axis. In recent years, it has become clear that in birds an adequate level of thyroid hormones (THs), i.e. thyroxine (T4) and triiodothyronine (T3), in blood circulation is of primary importance for normal female reproductive functions. In avian species, characterized by seasonal reproduction, THs are involved in the photoperiodic regulation of reproduction acting at the mediobasal hypothalamus. In domestic fowl, where the seasonality of reproduction has been eliminated, the role of THs in ovarian function is not fully elucidated. Recent studies have revealed that ovarian follicles of the laying hen express mRNAs of TH nuclear receptors (TRα and TRβ0) as well as integrin (αVβ3) plasma membrane receptors, indicating genomic and nongenomic action of THs in the chicken ovary. In vivo experiments carried out on laying hens have showed that the bolus injection of T3 decreases levels of luteinizing hormone (LH) and estradiol (E2) in blood, and a hyperthyroid state evoked by administration of T3 for few days diminishes LH, E2 and progesterone (P4) levels, reduces the weight of the ovary, induces atresia of preovulatory follicles and eventually causes stoppage of egg laying. In vitro studies have demonstrated that T3 decreases E2 secretion from white nonhierarchical follicles and the theca layer of yellow preovulatory follicles, while on the other hand, it elevates P4 production from the granulosa layer of these follicles. These effects have been associated with steroidogenic enzyme expression and cyclic AMP synthesis. This review summarizes the current knowledge concerning the role of THs in regulation of steroidogenesis in chicken ovarian follicles.
在所有脊椎动物中，包括鸟类，卵巢和卵泡的正常发育都受到生殖轴产生的激素的调节。近年来，人们已经清楚地认识到，鸟类血液中甲状腺激素（THs），即甲状腺素（T4）和三碘甲状腺原氨酸（T3）的适当水平对于正常的雌性生殖功能至关重要。在具有季节性繁殖特征的鸟类中，THs 参与光周期调节生殖作用于中脑基底部下丘脑。在繁殖季节性已被消除的家禽中，THs 在卵巢功能中的作用尚未完全阐明。最近的研究表明，产蛋母鸡的卵泡表达 TH 核受体（TRα 和 TRβ0）以及整合素（αVβ3）质膜受体的 mRNA，表明 THs 在鸡卵巢中的基因组和非基因组作用。对产蛋母鸡进行的体内实验表明，T3 的单次注射会降低血液中促黄体生成激素（LH）和雌二醇（E2）的水平，而 T3 给药几天引起的甲状腺功能亢进状态会降低 LH、E2 和孕酮（P4）的水平，减少卵巢重量，诱导排卵前卵泡的闭锁，并最终导致产蛋停止。体外研究表明，T3 降低了白色无等级卵泡和黄色排卵前卵泡的外膜层中 E2 的分泌，而另一方面，它提高了这些卵泡的颗粒层中 P4 的产生。这些作用与甾体生成酶表达和环腺苷酸合成有关。这篇综述总结了目前关于 THs 调节鸡卵巢卵泡甾体生成的作用的知识。
