Foster D L, Lemons J A, Jaffe R B, Niswender G D
Endocrinology. 1975 Oct;97(4):985-94. doi: 10.1210/endo-97-4-985.
Patterns of circulating LH and FSH were examined during several 6-h periods in developing female sheep from 3 weeks of age through the first estrous cycles (30--40 weeks of age) and early pregnancy. With the onset of pulsatile LH secretion, beginning 11 weeks after birth, circulating LH increased to levels 2- to 5-fold greater than those observed in the adult. Thereafter, high and variable levels of circulating LH persisted through young adulthood when ovarian cyclicity including ovulation became manifest. Although prior to the initial estrus changes in frequency of LH release (number of LH discharges/6-h period) appeared to occur randomly from week to week, after first estrus, changes in frequency became predictable. During the early (day 1) and late (day 15) luteal phases of the first estrous cycles, when circulating progesterone was low (less than 0.6 ng/ml), the frequency of LH release was increased (5--7 discharges/6 h) while during the mid-luteal phase (day 7--12), when circulating progesterone was high (2--4 ng/ml), the frequency was diminished (0--2 discharges/6 h). Massive and sustained discharges of LH which resembled preovulatory surges were observed only shortly before first estrus. In contrast to the pulsatile release pattern of LH, concentrations of circulating FSH within the 6-h periods were relatively constant and within the range found in the adult. These findings lead to the following conclusions: a) changes in negative feedback control are not directly responsible for the onset of ovarian cyclicity in the sheep as indicated by the lack of differences in mean concentrations of circulating LH and FSH before and after first ovulation; b) the onset of the surge mode of gonadotropin secretion occurs only shortly before first ovulation; and c) progesterone may play an inhibitory role in regulating tonic LH secretion during the first estrous cycles.
在3周龄至首次发情周期（30 - 40周龄）以及怀孕早期的发育中的雌性绵羊的几个6小时时间段内，对循环中的促黄体生成素（LH）和促卵泡生成素（FSH）模式进行了检查。随着出生后11周开始出现LH脉冲式分泌，循环中的LH增加到比成年羊中观察到的水平高2至5倍。此后，在包括排卵在内的卵巢周期性出现之前，循环中的LH持续处于高水平且变化不定，直至成年早期。尽管在首次发情之前，LH释放频率（每6小时LH释放次数）的变化似乎每周都随机发生，但首次发情后，频率变化变得可预测。在第一个发情周期的早期（第1天）和晚期（第15天），当循环中的孕酮水平较低（低于0.6 ng/ml）时，LH释放频率增加（每6小时5 - 7次释放），而在黄体中期（第7 - 12天），当循环中的孕酮水平较高（2 - 4 ng/ml）时，频率降低（每6小时0 - 2次释放）。仅在首次发情前不久观察到类似于排卵前激增的大量且持续的LH释放。与LH的脉冲式释放模式相反，在6小时时间段内循环中的FSH浓度相对恒定，且在成年羊中发现的范围内。这些发现得出以下结论：a）如首次排卵前后循环中的LH和FSH平均浓度缺乏差异所示，负反馈控制的变化并非绵羊卵巢周期性开始的直接原因；b）促性腺激素分泌的激增模式仅在首次排卵前不久出现；c）孕酮可能在调节第一个发情周期中的LH基础分泌中起抑制作用。
