Webb R, Campbell B K, Garverick H A, Gong J G, Gutierrez C G, Armstrong D G
Division of Agriculture and Horticulture, School of Biological Sciences, University of Nottingham, Loughborough, Leicestershire, UK.
J Reprod Fertil Suppl. 1999;54:33-48.
Ovarian follicular growth and development is an integrated process encompassing both extraovarian signals, such as gonadotrophins and metabolic hormones, and intraovarian factors. Follicular development has been classified into gonadotrophin-independent and -dependent phases. In the latter, FSH provides the primary drive for follicular recruitment and LH is required for continued development of follicles to the preovulatory stage. A transient increase in circulating FSH precedes the recruitment of a group of follicles, and these recruited follicles are characterized by expression of mRNAs encoding P450scc and P450arom in granulosal cells. As follicles mature, there is a transfer of dependency from FSH to LH, which may be part of the mechanism(s) involved in selection of follicles for continued growth. Indeed, changes in the pattern of expression of mRNA for gonadotrophin receptors and steroid enzymes within follicular cells appear to be closely linked to changes in peripheral concentrations of gonadotrophins. The mechanism of selection of dominant follicles still requires clarification, but seems to be linked to the timing of mRNA expression encoding LHr and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) in granulosal cells. Additional intraovarian systems, including the ovarian IGF and activin/inhibin systems, also exert a role. For example, it appears that the development of follicular dominance in cows is associated with the FSH-dependent inhibition of the expression of mRNA encoding insulin-like growth factor binding protein 2 (IGFBP-2) in granulosal cells. In conclusion, the integration of these endocrine signals and intraovarian factors within follicles determines whether follicles continue to develop and become dominant or are diverted into apoptotic pathways leading to atresia.
卵巢卵泡的生长和发育是一个综合过程，既包括卵巢外信号，如促性腺激素和代谢激素，也包括卵巢内因素。卵泡发育已被分为不依赖促性腺激素和依赖促性腺激素两个阶段。在后者中，促卵泡激素（FSH）为卵泡募集提供主要驱动力，而促黄体生成素（LH）是卵泡持续发育至排卵前阶段所必需的。循环中FSH的短暂升高先于一组卵泡的募集，这些募集的卵泡的特征是颗粒细胞中编码细胞色素P450侧链裂解酶（P450scc）和芳香化酶（P450arom）的mRNA表达。随着卵泡成熟，依赖性从FSH转移到LH，这可能是参与选择继续生长卵泡的机制的一部分。事实上，卵泡细胞内促性腺激素受体和类固醇酶mRNA表达模式的变化似乎与外周促性腺激素浓度的变化密切相关。优势卵泡的选择机制仍需阐明，但似乎与颗粒细胞中编码促黄体生成素受体（LHr）和3β-羟基类固醇脱氢酶（3βHSD）的mRNA表达时间有关。其他卵巢内系统，包括卵巢胰岛素样生长因子（IGF）和激活素/抑制素系统，也发挥作用。例如，奶牛卵泡优势化的发展似乎与颗粒细胞中编码胰岛素样生长因子结合蛋白2（IGFBP-2）的mRNA表达受FSH依赖性抑制有关。总之，这些内分泌信号和卵泡内卵巢内因素的整合决定了卵泡是否继续发育并成为优势卵泡，还是转向导致闭锁的凋亡途径。
