Souza C J, Campbell B K, Baird D T
Department of Obstetrics & Gynaecology, University of Edinburgh, Centre for Reproductive Biology, Scotland.
Biol Reprod. 1997 Feb;56(2):483-8. doi: 10.1095/biolreprod56.2.483.
In this study, we investigated follicular dynamics and ovarian steroid secretion during the follicular and early luteal phases of the estrous cycle in sheep. Six Finn-Merino ewes with ovarian autotransplanted ovaries were monitored for 10 days during the follicular phase and subsequent early luteal phase after luteal regression was induced with cloprostenol (a potent analogue of prostaglandin F2alpha). Over this period, follicular diameter was measured by serial ultrasound scans, and the concentration of gonadotropins and steroids in ovarian venous blood was measured at intervals of 6-12 h. All animals had an LH surge (Day 0) 59 +/- 4.7 h after injection of cloprostenol. The ovulatory follicles were derived mainly from large antral follicles present at the time of injection of cloprostenol (5.1 +/- 0.4 mm; mean +/- SEM, n = 6), although in some animals recruitment of additional small follicles was observed after luteolysis. The concentration of FSH decreased during the follicular phase and peaked synchronously with the LH surge, while estradiol and androstenedione concentrations in ovarian venous plasma increased progressively from luteal regression to a maximum at the LH surge. The rise in concentration of FSH on Day 1 was followed by the growth of a new cohort of follicles. Follicular size and ovarian steroid secretion increased in a linear fashion from Day 1 to Day 3, with ovarian steroid secretion reaching a maximum when the first wave of luteal phase follicles achieved a diameter of 5 mm or more. On Day 4, steroid secretion began to decline without significant changes in follicular diameter, and a second wave of follicles emerged. We conclude that 1) the preovulatory follicles are usually derived from the large follicle population present at the time of luteal regression, but the sheep has the ability to promote smaller follicles if required; and 2) the second peak of FSH stimulates the development of large estrogenic follicles during the early luteal phase, but the period of functional dominance is shorter than the period of morphological dominance.
在本研究中，我们调查了绵羊发情周期卵泡期和黄体早期的卵泡动态及卵巢类固醇分泌情况。对6只自体移植卵巢的芬兰美利奴母羊，在卵泡期及用氯前列醇（一种高效前列腺素F2α类似物）诱导黄体退化后的随后黄体早期进行了为期10天的监测。在此期间，通过连续超声扫描测量卵泡直径，并每隔6 - 12小时测量一次卵巢静脉血中促性腺激素和类固醇的浓度。所有动物在注射氯前列醇后59±4.7小时出现促黄体生成素峰（第0天）。排卵卵泡主要来源于注射氯前列醇时存在的大卵泡（5.1±0.4毫米；平均值±标准误，n = 6），不过在一些动物中，黄体溶解后观察到有额外小卵泡的募集。卵泡期促卵泡素浓度下降，并与促黄体生成素峰同步达到峰值，而卵巢静脉血浆中雌二醇和雄烯二酮浓度从黄体退化到促黄体生成素峰时逐渐升高至最大值。第1天促卵泡素浓度升高后，新一批卵泡开始生长。从第1天到第3天，卵泡大小和卵巢类固醇分泌呈线性增加，当黄体期第一波卵泡直径达到5毫米或更大时，卵巢类固醇分泌达到最大值。第4天，类固醇分泌开始下降，卵泡直径无显著变化，并且出现了第二波卵泡。我们得出结论：1）排卵前卵泡通常来源于黄体退化时存在的大卵泡群体，但绵羊在需要时具有促进较小卵泡发育的能力；2）促卵泡素的第二个峰值刺激黄体早期大的雌激素生成卵泡的发育，但功能优势期短于形态优势期。
