Channing C P, Schaerf F W, Anderson L D, Tsafriri A
Int Rev Physiol. 1980;22:117-201.
Follicular maturation and development is a complex process of interrelated intra- and extraovarian events that ultimately lead to ovulation of a mature oocyte and transformation of the ruptured follicle into a corpus luteum. The primordial follicle consists of an immature oocyte arrested in the dictyate stage of meiosis, surrounded by a single layer of relatively undifferentiated granulosa cells. The oocyte remains in the immature state because of many factors, one of which is the oocyte maturation inhibitor (OMI) secreted by granulosa cells. The oocyte subsequently increases in size, and as the antrum forms it becomes surrounded by cumulus cells. The cumulus cells may be intimately involved in the action of O,I to arrest the oocyte in the immature state within the follicle, as well as the resumption of meiosis during the LH surge. The compartments of the follicle that change most dramatically during follicular maturation are the cells lining the follicle--the granulosa and thecal cells. Under the influence of estrogen and FSH, the granulosa cells proliferate and also acquire FSH receptors. At this time, the thecal compartment differentiates and surrounds the granulosa cells, but remains separated from them by a basement membrane. Steroid secretion by the antral follicle involves the interplay of androgens, estrogens, and progestins. Both the granulosa and thecal cell compartments contribute to follicular fluid and serum levels of steroids; the interaction of both cell types may be necessary for estrogen and progesterone secretion in some species. As a consequence of the presence of an elevated number of FSH receptors, the granulosa cells of the small antral follicle are able to respond to FSH in many ways, including increased cyclic AMP accumulation, activation of the aromatase system, and induction of LH receptors, which permits the granulosa cells to later respond to LH. The mechanism by which thecal cells acquire their LH receptors is presently unknown. The granulosa cells of the follicle may indirectly control their own maturation and the number of follicles maturing through the secretion of follicular inhibin, which decreases the pituitary output of FSH. Even though the granulosa cells have acquired large numbers of LH receptors, they are prevented from luteinizing prematurely by factors in follicular fluid, including estrogen and a luteinizing inhibitor (LI). As serum LH levels increase during the preovulatory LH surge, a number of events occur: resumption of oocyte meiosis, transformation of the steroid enzyme complex from estrogen to progesterone secretion, follicular rupture, and formation of the corpus luteum. Granulosa cells form the bulk of the corpus luteum, which secretes elevated amounts of progesterone for a fixed time period depending on the species. Before ovulation the preovulatory follicle must be exposed to and respond to adequate LH and FSH levels in order for the eventual corpus luteum to secrete elevated amounts of progesterone for its normal lifespan...
卵泡成熟和发育是一个复杂的过程，涉及卵巢内和卵巢外相互关联的一系列事件，最终导致成熟卵母细胞排卵，并使破裂的卵泡转化为黄体。原始卵泡由一个停滞在减数分裂双线期的未成熟卵母细胞组成，周围环绕着单层相对未分化的颗粒细胞。由于多种因素，卵母细胞保持未成熟状态，其中之一是颗粒细胞分泌的卵母细胞成熟抑制因子（OMI）。随后卵母细胞体积增大，随着卵泡腔形成，它被卵丘细胞包围。卵丘细胞可能密切参与了OMI的作用，使卵母细胞在卵泡内处于未成熟状态，以及在促黄体生成素（LH）峰期间减数分裂的恢复。在卵泡成熟过程中变化最为显著的卵泡组成部分是卵泡内衬细胞——颗粒细胞和卵泡膜细胞。在雌激素和促卵泡生成素（FSH）的影响下，颗粒细胞增殖并获得FSH受体。此时，卵泡膜部分分化并包围颗粒细胞，但仍通过基膜与颗粒细胞分隔开。窦状卵泡的类固醇分泌涉及雄激素、雌激素和孕激素的相互作用。颗粒细胞和卵泡膜细胞部分都对卵泡液和血清中的类固醇水平有贡献；在某些物种中，两种细胞类型的相互作用可能是雌激素和孕激素分泌所必需的。由于存在大量FSH受体，小窦状卵泡的颗粒细胞能够以多种方式对FSH作出反应，包括增加环磷酸腺苷（cAMP）积累、激活芳香化酶系统以及诱导LH受体，这使得颗粒细胞随后能够对LH作出反应。卵泡膜细胞获得LH受体的机制目前尚不清楚。卵泡的颗粒细胞可能通过分泌卵泡抑制素间接控制自身的成熟以及成熟卵泡的数量，卵泡抑制素会降低垂体FSH的分泌量。尽管颗粒细胞已经获得了大量LH受体，但卵泡液中的因素，包括雌激素和一种黄体化抑制因子（LI），可防止它们过早黄体化。在排卵前LH峰期间，随着血清LH水平升高，会发生一系列事件：卵母细胞减数分裂恢复、类固醇酶复合物从分泌雌激素转变为分泌孕激素、卵泡破裂以及黄体形成。颗粒细胞构成黄体的主体，黄体在一定时间段内分泌大量孕激素，具体时间因物种而异。在排卵前，排卵前卵泡必须暴露于足够水平的LH和FSH并对其作出反应，以便最终形成的黄体在其正常寿命期间分泌大量孕激素……
