Brann D W, O'Conner J L, Wade M F, Zamorano P L, Mahesh V B
Department of Physiology and Endocrinology, Medical College of Georgia, Augusta 30912-3000.
J Steroid Biochem Mol Biol. 1993 Oct;46(4):427-37. doi: 10.1016/0960-0760(93)90097-g.
In a previous study we demonstrated that in the ovariectomized estrogen-primed immature rat, progesterone induced a gonadotropin surge while the gonadotropin mRNA subunit levels were either suppressed or unaltered. This observation has now been confirmed using more frequent time points. Progesterone administered at 0900 h was found to suppress LH-beta mRNA levels at 1300, 1400, and 0800 h the next day, with no subsequent effects at 1000, 1200 or 1600 h. FSH-beta mRNA levels were unaffected by progesterone except for a slight elevation at 1400 h and a suppression at 0800 h. Progesterone was either suppressive or had no effect on alpha mRNA levels. Since elevations in LH-beta and FSH-beta mRNA levels were observed in the cycling rat, the observed differences in the ovariectomized estrogen-primed rat could be due to a higher basal synthesis occurring due to ovariectomy. This was indeed the case because LH-beta and FSH-beta mRNA levels were 3.7- and 42.7-fold higher in such animals as compared to intact estrogen-primed rats. In contrast to the ovariectomized estrogen-primed rats, in intact estrogen-primed rats LH-beta mRNA levels were increased at 1000 h and FSH-beta mRNA levels were increased at 1000, 1200 and 1300 h after the administration of progesterone. In pregnant mare's serum gonadotropin-primed immature rats, LH-beta, FSH-beta and alpha-subunit mRNA levels were significantly elevated at 1800 and 2000 h, paralleling the serum LH and FSH surge. The progesterone antagonist RU486 (0.2 and 1.0 mg) significantly reduced serum LH and FSH levels at 2000 h. The lower dose reduced LH-beta and alpha-subunit mRNA levels at 2000 h and FSH-beta mRNA levels at 1800 h. The higher dose caused an increase in LH-beta mRNA levels at 1200 and 1800 h and a decrease in FSH-beta mRNA levels at 1800 and 2000 h. In conclusion, the present study provides evidence that preovulatory progesterone plays an important role in the increase in FSH-beta mRNA levels as well as the release of LH and FSH during the normal preovulatory gonadotropin surge. This relationship appears to be dependent on the ongoing rate of synthesis because this does not occur in the ovariectomized estrogen-primed rat in which synthesis is at a high basal level. Furthermore, the correlation with FSH appears to be tighter as compared to LH.
在之前的一项研究中，我们证明，在切除卵巢并用雌激素预处理的未成熟大鼠中，孕酮可诱导促性腺激素激增，而促性腺激素亚基的mRNA水平要么受到抑制，要么未发生改变。现在通过更频繁的时间点已证实了这一观察结果。发现在09:00给予的孕酮可在次日13:00、14:00和08:00抑制LH-β mRNA水平，在10:00、12:00或16:00无后续影响。FSH-β mRNA水平除在14:00略有升高和在08:00受到抑制外，不受孕酮影响。孕酮对α mRNA水平要么有抑制作用，要么无影响。由于在发情周期的大鼠中观察到LH-β和FSH-β mRNA水平升高，在切除卵巢并用雌激素预处理的大鼠中观察到的差异可能是由于卵巢切除导致基础合成增加所致。实际情况确实如此，因为与完整的用雌激素预处理的大鼠相比，此类动物中LH-β和FSH-β mRNA水平分别高3.7倍和42.7倍。与切除卵巢并用雌激素预处理的大鼠相反，在完整的用雌激素预处理的大鼠中，给予孕酮后，LH-β mRNA水平在10:00升高，FSH-β mRNA水平在10:00、12:00和13:00升高。在用孕马血清促性腺激素预处理的未成熟大鼠中，LH-β、FSH-β和α亚基的mRNA水平在18:00和20:00显著升高，与血清LH和FSH激增同步。孕酮拮抗剂RU486（0.2和1.0毫克）在20:00显著降低血清LH和FSH水平。较低剂量在20:00降低LH-β和α亚基的mRNA水平，在18:00降低FSH-β mRNA水平。较高剂量导致12:00和18:00 LH-β mRNA水平升高，18:00和20:00 FSH-β mRNA水平降低。总之，本研究提供了证据，表明排卵前的孕酮在正常排卵前促性腺激素激增期间FSH-β mRNA水平升高以及LH和FSH释放中起重要作用。这种关系似乎取决于正在进行的合成速率，因为在切除卵巢并用雌激素预处理的大鼠中不会发生这种情况，在该大鼠中合成处于高基础水平。此外，与LH相比，与FSH的相关性似乎更紧密。
