Interralation between various hormones for egg production in birds

家禽是研究颗粒细胞和膜细胞在卵巢类固醇合成中相互作用的理想实验模型，主要有两个原因。首先，卵泡按不同的等级顺序排列，根据先前排卵的卵泡的产卵时间，可以很容易地预测它们排卵的准确时间。其次，卵泡壁、颗粒细胞和膜细胞的主要成分可以很容易地相互分离。所有的卵泡都暴露在每天的黄体生成素激增中，但每天只有最大的卵泡(FL)排卵。这归因于F1的孕酮合成能力对黄体生成素的反应。通过对日本鹌鹑卵巢细胞类固醇合成的体外研究，阐明了F1代与小卵泡的不同之处：1.促黄体生成素刺激时，F1代颗粒细胞的孕酮水平是未刺激时的10倍，而小卵泡颗粒细胞的孕酮水平增加了不到一倍。在小卵泡的囊膜细胞中，催化孕酮转化为17-羟孕酮的17-α-羟基酶活性很高。F_1代卵泡膜细胞和所有卵泡的颗粒细胞基本上不含该酶。C17-C20裂解酶的活性也有相似的组织分布，C17-C20裂解酶将17-α-羟孕酮转化为雄烯二酮。这些发现表明，当卵泡变大时，不仅颗粒细胞获得了对黄体生成素的反应机制，而且膜细胞也失去了将孕酮代谢为其他类固醇的酶活性。在活体研究中，对切除了脑下垂体的鹌鹑进行的研究表明，这些细胞突触受到促性腺激素的影响。

Domestic birds are an ideal experimental model for the study of the inter-action of the granulosa and theca cells in ovarian steroidogenesis, for two main reasons. First, the follicles are arranged in a distinct hierarchical order and their exact time to ovulation can easily be predicted from the time of oviposition of the previously ovulated follicle. Second, major components of the follicle walls, the granulosa and theca cells can be easily separated from one another.All follicles are exposed to a daily surge of LH, but only the largest follicle (FL) ovulates each day. This has been attributed to the ability of progesterone synthesis of F1 in response to LH. From the in vitro studies on steroidogenesis by ovarian cells of the Japanese quail, the following differences between F1 and small follicles have been clarifed:1. When stimulated with LH, the granulosa cells of F1 responded with a tenfold increase over unstimulated progesterone levels, whereas progesterone production in the granulosa cells of small follicles less than doubled.2. Activity of 17<alpha>-hydroxylase, which catalyzes the conversion of progesterone to 17<alpha>-hydroxyprogesterone, was high in the theca cells of small follicles. the theca cells of F1 and the granulosa cells of all follicles examined were essentially devoid of this enzyme. Similar tissue distribution was found for the activity of C17-C20 lyase, which convert 17<alpha>-hydroxyprogesterone to androstenedione.These findings indicate that when the follicle becomes the largest, not only the granulosa cells acquire the machinery for response to LH, but also the theca cells lose the enzyme activities, which metabolize progesterone to other steroids. In vivo studies using hypophysectomized quail reveal that these cellular chnges are under the influence of gonadotropins.