Tsafriri A, Pomerantz S H
Symp Soc Exp Biol. 1984;38:25-43.
The first meiotic maturation division of mammalian oocytes is initiated in the embryo or during the early postnatal period. However, when the germ cells reach the diplotene stage the meiotic process is arrested. Meiosis is normally kept in abeyance up to a short period prior to ovulation, when the process is resumed in preovulatory follicles. Resumption of meiosis is studied in mammalian oocytes mainly in two dissimilar in vitro models, isolated oocytes maturing spontaneously in culture and hormone-induced maturation of follicle-enclosed oocytes. A third approach, namely, co-culture of oocytes with follicular constituents was adopted in order to test the role of follicular components in the control of meiosis. Such studies demonstrated an inhibitory action of granulosa cells, granulosa-cell conditioned medium and of follicular fluid (FF1) upon the spontaneous maturation of co-cultured oocytes. By contrast, theca tissue was without effect on meiosis. Addition of luteinizing hormone (LH) to co-cultures of rat granulosa cells and rat oocytes induced resumption of meiosis, as it does in vivo or in vitro in follicle-enclosed oocytes. It is therefore suggested that within antral follicles meiosis is held in abeyance by a granulosa cell product, the inhibitor of oocyte maturation (OMI). Further studies led to the conclusion that OMI is not species specific, that its production by granulosa cells is enhanced by follicle stimulating hormone (FSH) and that its concentration in FF1 is dependent upon the development of the follicle and not the stage of the oestrous cycle. OMI appears to be a peptide of less than 2000 Da. Its action on the oocyte appears to be mediated, at least partially, by cumulus cells and is potentiated by cyclic AMP. Since OMI activity has been demonstrated only in antral follicles, we examined the development of the ability of rat oocytes to undergo spontaneous maturation during their growth phase in preantral follicles. We have found that the ability of rat oocytes to resume maturation ('meiotic competence') is acquired between days 20-26 post partum. By the use of hypophysectomy on day 15 of life and by treatment with hormones and inhibitors we demonstrated that the acquisition of meiotic competence is dependent upon FSH stimulation and that it is mediated, at least partially, by ovarian oestrogen production. The findings that oocytes from preantral follicles are meiotically incompetent suggests that the physiological role of follicular OMI is limited only to antral follicles i.e. when the oocytes acquire meiotic competence.(ABSTRACT TRUNCATED AT 400 WORDS)
哺乳动物卵母细胞的第一次减数分裂成熟分裂始于胚胎期或出生后早期。然而，当生殖细胞到达双线期时，减数分裂过程会停滞。减数分裂通常会暂停，直到排卵前的短时间，此时该过程在排卵前卵泡中恢复。哺乳动物卵母细胞减数分裂的恢复主要在两种不同的体外模型中进行研究，即培养中自发成熟的分离卵母细胞和卵泡包裹的卵母细胞的激素诱导成熟。为了测试卵泡成分在减数分裂控制中的作用，采用了第三种方法，即卵母细胞与卵泡成分的共培养。此类研究表明，颗粒细胞、颗粒细胞条件培养基和卵泡液（FF1）对共培养卵母细胞的自发成熟具有抑制作用。相比之下，卵泡膜组织对减数分裂没有影响。向大鼠颗粒细胞和大鼠卵母细胞的共培养物中添加促黄体生成素（LH）可诱导减数分裂恢复，就如同其在体内或体外对卵泡包裹的卵母细胞所起的作用一样。因此，有人提出在有腔卵泡内，减数分裂由颗粒细胞产物——卵母细胞成熟抑制剂（OMI）维持暂停状态。进一步的研究得出结论，OMI不具有物种特异性，颗粒细胞对其产生受促卵泡激素（FSH）增强，且其在FF1中的浓度取决于卵泡的发育而非发情周期的阶段。OMI似乎是一种分子量小于2000 Da的肽。它对卵母细胞的作用似乎至少部分是由卵丘细胞介导的，并且被环磷酸腺苷增强。由于仅在有腔卵泡中证明了OMI活性，我们研究了大鼠卵母细胞在窦前卵泡生长阶段进行自发成熟的能力的发育情况。我们发现大鼠卵母细胞恢复成熟的能力（“减数分裂能力”）在产后第20 - 26天获得。通过在出生后第15天进行垂体切除以及用激素和抑制剂进行处理，我们证明减数分裂能力的获得依赖于FSH刺激，并且至少部分是由卵巢雌激素的产生介导的。来自窦前卵泡的卵母细胞减数分裂无能力这一发现表明，卵泡OMI的生理作用仅限于有腔卵泡，即当卵母细胞获得减数分裂能力时。（摘要截短至400字）
