Regulation mechanisms of transcription of sex steroidogenic enzymes during follicular growth in the chicken.

在F1预期排卵前20 h和3 h，分别测定鸡排卵期最大卵泡（F1- f4）离体颗粒、内膜和外膜中雌二醇(E)、睾酮(T)和孕酮(P)的浓度以及编码P450_< 17α >羟化酶（P450_< 17α >）和P450_<芳香化酶> (P450_<arom>)的1.9 kb和4.0 kb mRNA水平。在颗粒层，E和T浓度在整个卵泡生长期间保持较低水平，而在F2和F1卵泡排卵前3小时P浓度较高。雌二醇水平在最小（F4）卵泡的卵膜内和卵泡外最高，随着卵泡的生长逐渐降低。较不成熟的F4-F2卵泡内膜和颗粒中睾酮含量高于最成熟的（F1）卵泡，而卵泡外膜中含有少量的T.P仅在颗粒组织中有显著的量，在F2和F1卵泡中在排卵前3小时达到峰值，此时血浆类固醇水平也显著升高。P450_< 17α >主要在内腔表达，而外腔中P450_< 17α >的mRNA水平反映了E在该室的分布模式。这两个基因在颗粒组织中的表达非常低，在卵泡生长过程中保持不变。以上结果表明，卵泡生长过程中，鸡卵巢E和T的合成至少部分受卵泡内、外两层P450_<17alpha>和P450_<arom> mRNA水平的调控。

Concentrations of estradiol (E), testosterone (T) and progesterone (P), and levels of the 1.9-kb and 4.0-kb mRNA encoding P450_<17alpha> hydroxylase(P450_<17alpha>) and P450_<aromatase> (P450_<arom>), respectively, were measured in the isolated granulosa, theca interna and theca externa of the largest preovulatory (F1-F4) follicles of the chicken 20 h and 3 h before expected ovulation of F1. In the granulosa layr, E and T concentrations remained low throughout this period of follicular growth, whereas P concentrations were high 3 h before ovulation in F2 and F1 follicles. Estradiol levels were highest in the theca interna and externa of the amallest (F4) follicle, decreasing progressively with follicular growth. Testosterone content of theca interna and granulosa was greater in less mature F4-F2 follicles than that found in the most mature (F1) follicle, whereas theca externa contained little T.P was quantifiable in significant amounts only in granulosa tissue, peaking in F2 and F1 follicles at 3 h before ovulation, at which time plasma levels of steroids also rose significantly. P450_<17alpha> was expressed mainly in theca interna, whereas P450_<arom> mRNA levels found in theca externa refiected the pattern of E in this compartment. Expression of these two genes was very low in granulosa tissue, remaining unchanged during follicular growth. These results indicate that E and T synthesis in the chicken ovary is regulated, at least in part, at mRNA levels of P450_<17alpha> and P450_<arom> in the theca interna and theca externa layrs during follicular growth.