Urbanski H F, Ojeda S R
Endocrinology. 1985 Aug;117(2):638-43. doi: 10.1210/endo-117-2-638.
We have previously demonstrated changes in the episodic pattern of LH secretion in female rats as they approach first ovulation. In the present study, ovaries were taken from peripubertal rats and perifused in vitro with a medium containing FSH and LH. The concentration of FSH in the medium was kept constantly low, whereas the concentration of LH was modulated, simulating as closely as possible the various episodic secretory profiles previously observed in vivo. Medium from the perifusion chambers was collected every 10 min for 5 h and assayed for progesterone (P) and 17 beta-estradiol (E2). Exposure of the ovaries to low amplitude LH pulses (20 ng/ml; comparable to those found in the plasma of peripubertal rats during the morning) did not elicit a significant steroidogenic response. On the other hand, exposure to large amplitude LH pulses (80 ng/ml; as seen during the afternoon) led to a marked increase in the output of both P and E2. Similarly, increased steroid secretion occurred when ovaries were exposed to a 2-h minisurge of LH (160 ng/ml) or to a minisurge preceded by three large amplitude pulses (as seen in some animals during the afternoons of the peripubertal period). Continuous exposure to LH at concentrations similar to either the large amplitude pulses or the LH minisurge increased P and E2 release. However, the increase was not significantly larger than that produced by the discontinuous LH perifusion patterns, even though the total amount of LH reaching the ovaries during the 5-h perifusion period was considerably greater. The results show that episodic LH secretion is functionally much more efficient at eliciting release of P and E2 from immature ovaries than is continuous LH secretion. Furthermore, they strongly suggest that changes in the LH secretory pulse patterns, as seen in vivo close to the time of puberty, are fundamental for the activation of ovarian steroidogenesis that leads to the first preovulatory surge of gonadotropins.
我们之前已经证明，雌性大鼠在接近首次排卵时，促黄体生成素（LH）分泌的 episodic 模式会发生变化。在本研究中，从青春期前大鼠获取卵巢，并在体外使用含有促卵泡生成素（FSH）和 LH 的培养基进行灌流。培养基中 FSH 的浓度保持在较低水平，而 LH 的浓度则进行调节，尽可能模拟先前在体内观察到的各种 episodic 分泌模式。每隔 10 分钟从灌流室收集培养基，持续 5 小时，并测定孕酮（P）和 17β - 雌二醇（E2）。将卵巢暴露于低幅度 LH 脉冲（20 纳克/毫升；与青春期前大鼠早晨血浆中发现的类似）并未引发显著的类固醇生成反应。另一方面，暴露于高幅度 LH 脉冲（80 纳克/毫升；下午所见）导致 P 和 E2 的输出显著增加。同样，当卵巢暴露于 2 小时的 LH 小高峰（160 纳克/毫升）或在三个高幅度脉冲之前出现的小高峰（青春期前阶段某些动物下午所见）时，类固醇分泌增加。持续暴露于与高幅度脉冲或 LH 小高峰浓度相似的 LH 会增加 P 和 E2 的释放。然而，尽管在 5 小时灌流期间到达卵巢的 LH 总量要大得多，但这种增加并不比不连续的 LH 灌流模式产生的增加显著更大。结果表明，与持续的 LH 分泌相比，episodic LH 分泌在促使未成熟卵巢释放 P 和 E2 方面在功能上效率更高。此外，它们强烈表明，在青春期前后体内观察到的 LH 分泌脉冲模式的变化对于激活卵巢类固醇生成至关重要，而卵巢类固醇生成会导致促性腺激素的首次排卵前高峰。
