CHANGES IN THE SECRETION OF LH PULSES, FSH AND PROLACTIN DURING THE PREOVULATORY PHASE OF THE ESTROUS-CYCLE OF THE EWE AND THE INFLUENCE OF TREATMENT WITH BOVINE FOLLICULAR-FLUID DURING THE LUTEAL PHASE
CHANGES IN THE SECRETION OF LH PULSES, FSH AND PROLACTIN DURING THE PREOVULATORY PHASE OF THE ESTROUS-CYCLE OF THE EWE AND THE INFLUENCE OF TREATMENT WITH BOVINE FOLLICULAR-FLUID DURING THE LUTEAL PHASE
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DOI：
10.1677/joe.0.1160123
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发表时间：
1988-01-01
影响因子：
4
通讯作者：
MCNEILLY, AS
中科院分区：
文献类型：
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作者：
WALLACE, JM;MARTIN, GB;MCNEILLY, AS
以前已经表明，在整个发情周期的黄体期用牛卵泡液（bFF）处理母羊可降低FSH的血浆水平，但可增加LH脉冲的频率和幅度。在这些条件下，卵泡生长到最大直径为2.7 mm，释放雌二醇的能力降低。我们研究了促性腺激素信号控制卵泡发育的正常周期母羊的性质，并调查了以前暴露于bFF对这些信号和卵泡对它们的反应的影响。对照组母羊（n = 7）静脉注射9 ml牛血清，处理组母羊从黄体期第1天至第10天（第0天=发情期）每天注射9 ml bFF两次。母羊注射前列腺素类似物在第11天的周期，以诱导黄体溶解和促性腺激素的模式进行了研究，从这些动物的血液采样，每10分钟长达72小时，在随后的卵泡期。黄体溶解后（以及bFF治疗结束），两组的LH脉冲频率均迅速增加，并在6小时内达到1次脉冲/小时。此后，脉冲频率略有增加，并在LH峰开始时达到1脉冲/50分钟。该模式不受既往bFF治疗的影响。在对照母羊中，LH脉冲的幅度在黄体溶解后或在卵泡期的任何时间都没有显著变化，而FSH水平缓慢下降，直到激增开始。另一方面，在处理的母羊中，在黄体溶解时bFF处理结束后，LH脉冲幅度和FSH浓度立即增加，并且它们分别在24和16 h内保持高于对照水平。两组的血浆催乳素水平在黄体溶解前后似乎没有变化，但显示出明显的昼夜节律（中午前后最低，午夜前后最高）。与对照组相比，bFF处理组母羊的催乳素浓度显著（P < 0.001）降低，排卵前峰值延迟并降低。bFF处理也显著（P < 0.01）延迟了发情的开始，但排卵率在组间没有差异。此外，组内或组间比较显示，卵泡期血浆LH分泌的任何变量与随后的排卵率之间均无显著关系。这些观察结果提供了母羊卵泡期促性腺激素模式的完整描述，并证实了LH脉冲频率增加是卵泡生长的主要驱动力，最终导致排卵。另一方面，卵泡期LH分泌模式对排卵率有任何影响似乎是最不可能的。FSH水平在排卵前高峰期下降，可能是外周雌激素（和/或雌二醇）水平升高的结果。我们还预计LH脉冲幅度在卵泡期下降，因为有人提出脉冲幅度也受雌激素控制。没有任何显着的幅度下降表明，从卵巢切除母羊的研究中得出的LH分泌控制的假设需要进一步验证完整的母羊。bFF对催乳素水平的影响可能反映了这些母羊小卵泡分泌雌二醇的速率较低。
It has previously been shown that treatment of ewes with bovine follicular fluid (bFF) throughout the luteal phase of the oestrous cycle lowers plasma levels of FSH but increases the frequency and amplitude of the pulses of LH. Under these conditions, ovarian follicles grow to a maximum diameter of 2.7 mm and have a reduced capacity to release oestradiol. We have examined the nature of the gonadotrophin signals controlling follicular development in the normally cycling ewe and have investigated the effects of previous exposure to bFF on these signals and the follicular responses to them. Control ewes (n = 7) were injected i.v. with 9 ml bovine serum and treated ewes were injected with 9 ml bFF, twice daily from days 1 to 10 of the luteal phase (day 0 = oestrus). The ewes were injected with prostaglandin analogue on day 11 of the cycle to induce luteolysis and the gonadotrophin patterns were studied in blood sampled from these animals every 10 min for up to 72 h during the subsequent follicular phase. Following luteolysis (and the end of bFF treatment), LH pulse frequency increased rapidly in both groups and reached 1 pulse/h within 6 h. Thereafter, pulse frequency increased marginally and reached 1 pulse/50 min by the onset of the LH surge. This pattern was not affected by previous treatment with bFF. In the control ewes, the amplitude of the LH pulses did not change significantly following luteolysis or at any time during the follicular phase, while the levels of FSH declined slowly until the onset of the surge. In the treated ewes, on the other hand, there was an immediate increase in both LH pulse amplitude and the concentration of FSH immediately after the end of bFF treatment at luteolysis, and they remained above control levels for 24 and 16 h respectively. Plasma prolactin levels did not appear to change around the time of luteolysis but showed a marked and significant diurnal rhythm (nadir around noon and peak around midnight) in both groups. The concentrations of prolactin were significantly (P < 0.001) lower and the preovulatory peak was delayed and reduced in the bFF-treated ewes relative to controls. The onset of oestrus was also significantly (P < 0.01) delayed by bFF treatment, but the ovulation rates did not differ between the groups. Furthermore, comparisons within or between groups revealed no significant relationships between any of the variables of plasma LH secretion during the follicular phase and the subsequent ovulation rate. These observations provide a complete description of gonadotrophin patterns during the follicular phase of the ewe and confirm the suggestion that an increase in LH pulse frequency is the major driving force behind the follicular growth that ultimately leads to ovulation. On the other hand, it appears most unlikely that the pattern of LH secretion during the follicular phase has any influence on ovulation rate. The levels of FSH declined in the period leading up to the preovulatory surge, presumably as a consequence of rising peripheral levels of oestrogen (and/or inhibin). We also expected LH pulse amplitude to decline during the follicular phase because it has been proposed that pulse amplitude is also controlled by oestrogen. The absence of any significant fall in amplitude suggests that hypotheses about the control of LH secretion drawn from studies with ovariectomized ewes require further verification the intact ewe. The effect of bFF on prolactin levels probably reflects the low rates of secretion of oestradiol by the small ovarian follicles in these ewes.