OVARIAN FOLLICULAR-GROWTH AND DEVELOPMENT IN MAMMALS
OVARIAN FOLLICULAR-GROWTH AND DEVELOPMENT IN MAMMALS
复制标题
DOI：
10.1095/biolreprod50.2.225
复制
发表时间：
1994-02-01
影响因子：
3.6
通讯作者：
FORTUNE, JE
中科院分区：
文献类型：
--
作者：
FORTUNE, JE
来自几个物种的证据表明，卵泡生长的初始阶段进行得非常缓慢。相比之下，窦腔形成后的阶段要快得多。闭锁似乎是最普遍的卵泡接近大小，他们可以招募潜在的排卵。虽然大多数卵泡在这一阶段闭锁，但仍有少数卵泡被招募成一群或一波卵泡，这些卵泡在闭锁正常发生的阶段之后继续生长。接下来，选择一个物种特定数量的卵泡作为优势。在一些物种（如大鼠、灵长类动物、猪）中，优势卵泡只在卵泡期发育，并且注定要排卵。在另一组物种（如牛、羊、马）中，招募、选择和优势会定期发生，但只有在卵泡期存在的优势卵泡才会排卵。有证据表明，允许一些卵泡被招募用于潜在优势/排卵的机制是基础卵泡刺激素的小幅升高，偶然发生在卵泡通常开始闭锁的时候。一些再生的卵泡仅在短时间内免于闭锁。只有从招募的卵泡中选出的优势卵泡才能生长到排卵期或接近排卵期的大小。是什么决定了哪个卵泡成为优势尚不清楚，但优势似乎是通过优势卵泡的产物对循环FSH的负反馈效应来维持的。选择和优势是伴随着鞘细胞产生雄激素和颗粒细胞芳香化雄激素为雌二醇的能力的逐渐增加。卵泡期血浆LH的小幅升高似乎是这些变化的必要条件。对大鼠和牛的实验结果表明，卵泡雌激素合成能力的增强是由适当的类固醇生成酶信使RNA的增加介导的。LH/FSH激增通过减少雄激素和雌二醇的产生，增加卵泡分泌黄体酮的能力，从根本上改变了卵泡类固醇的生成。这些类固醇生成模式的变化与报道的类固醇生成酶mRNA水平的变化并不完全一致。虽然现在对卵泡发育的动力学和卵泡分化时的功能变化有了很多了解，但关于卵泡发育的一些核心问题仍有待回答。我们仍然不知道为什么卵泡离开休眠池，为什么只有一些被招募的卵泡被选择为优势。此外，关于促性腺激素与卵泡细胞之间以及卵泡细胞与卵母细胞之间的相互作用在卵泡分化的各个阶段中所起的作用，还有很多需要了解的。
Evidence from several species indicates that the initial stages of follicular growth proceed very slowly. In contrast, the stages after antrum formation are much more rapid. Atresia seems to be most prevalent as follicles approach the size at which they could be recruited for potential ovulation. Although most follicles become atretic around that stage, a few are recruited into a cohort or wave of follicles that continue to grow beyond the stage at which atresia normally occurs. Next, a species-specific number of follicles is selected for dominance. In some species (e.g. rats, primates, pigs), dominant follicles develop only during the follicular phase and are thug destined for ovulation In another group of species (e.g. cattle, sheep, horses), recruitment, selection, and dominance occur at regular intervals, but only the dominant follicle present during the follicular phase ovulates. There is evidence that the mechanism that allows some follicles to be recruited for potential dominance/ovulation is a small elevation in basal FSH that, by chance, occurs around the time the follicle would normally begin atresia. Some recruited follicles are saved from atresia for only a short time. Only the dominant follicle(s) selected from among the recruited follicles grows to ovulatory or near-ovulatory size. What determines which follicle(s) becomes dominant is not known, but dominance appears to be maintained by negative feedback effects of products of the dominant follicle on circulating FSH.Selection and dominance are accompanied by progressive increases in the ability of thecal cells to produce androgen and granulosa cells to aromatize androgen to estradiol. A small rise in plasma LH during the follicular phase seems necessary for these changes. Results of experiments with rats and cattle indicate that the enhanced estrogen-synthesizing capacity of ovulatory follicles is mediated by increases in messenger RNA for appropriate steroidogenic enzymes. The LH/FSH surge radically changes follicular steroidogenesis by decreasing androgen and estradiol production, and increasing follicular capacity to secrete progesterone. These shifts in steroidogenic patterns are not completely consistent with reported changes in mRNA levels for steroidogenic enzymes.Although much is now known about the dynamics of follicular development and about functional changes as follicles differentiate, some central questions about follicular development remain to be answered. We still do not know why follicles leave the resting pool and why only some recruited follicles are selected for dominance. In addition, there is still much to be learned about the roles of interactions between the gonadotropins and follicular cells, and between follicular cells and the oocyte, in the various stages of follicular differentiation.