Sakurai H, Adams B M, Oberbauer A M, Adams T E
Department of Animal Science, University of California, Davis 95616.
Biol Reprod. 1993 Mar;48(3):683-91. doi: 10.1095/biolreprod48.3.683.
Gonadotropin secretion during continuous infusion of estradiol (E2; 5 micrograms/h, i.v.) and pulsatile delivery of GnRH was assessed in orchidectomized sheep (wethers). Wethers received 200 ng GnRH per hourly pulse during the first 12 h of E2 infusion. During the final 36 h of infusion, animals (n = 6/group) received 0, 200, 400, 800, or 1600 ng GnRH/h pulse. Amplitude shift to 1600 ng GnRH/h pulse induced preovulatory surge-like secretion of LH in animals receiving concurrent E2 infusion. In the absence of E2, the same change in GnRH amplitude did not significantly affect serum concentrations of LH. Full expression of the GnRH-induced surge of LH in wethers required prior exposure to E2, but was not dependent on pretreatment with low-amplitude GnRH stimulus. In a companion experiment, anterior pituitary tissue was collected from E2-treated wethers 0, 3, 6, 12, or 24 h after initiation of episodic GnRH delivery (1600 ng/h pulse). Treatment with E2 induced a 5-fold increase in GnRH receptor concentration. The tissue concentration of GnRH receptor was depressed (p < 0.05) within 6 h of initiation of high-amplitude GnRH stimulation and remained depressed for the duration of GnRH delivery. Tissue stores of LH were increased (P < 0.05) by E2 and reduced (p < 0.05) after 3 h of high-amplitude GnRH stimulation. In contrast, tissue stores of FSH were reduced (p < 0.05) by both E2 alone and E2 with concurrent high-amplitude GnRH stimulation. The concentration of mRNA for the FSH beta subunit, but not for the alpha or LH beta subunits, was reduced (p < 0.05) by E2.(ABSTRACT TRUNCATED AT 250 WORDS)
在去势公羊中评估了持续输注雌二醇（E2；5微克/小时，静脉注射）和脉冲式释放促性腺激素释放激素（GnRH）期间的促性腺激素分泌情况。在E2输注的前12小时，公羊每小时脉冲接受200纳克GnRH。在输注的最后36小时，动物（每组n = 6）每小时脉冲分别接受0、200、400、800或1600纳克GnRH。在同时接受E2输注的动物中，将GnRH脉冲幅度提高到1600纳克/小时可诱导促黄体生成素（LH）出现类似排卵前高峰的分泌。在没有E2的情况下，GnRH幅度的相同变化对LH的血清浓度没有显著影响。公羊中GnRH诱导的LH高峰的充分表达需要事先接触E2，但不依赖于低幅度GnRH刺激的预处理。在一项配套实验中，在开始间歇性GnRH释放（1600纳克/小时脉冲）后0、3、6、12或24小时，从接受E2治疗的公羊中采集垂体前叶组织。E2治疗使GnRH受体浓度增加了5倍。在高幅度GnRH刺激开始后6小时内，GnRH受体的组织浓度降低（p < 0.05），并在GnRH释放期间一直保持降低。E2使LH的组织储存量增加（P < 0.05），在高幅度GnRH刺激3小时后降低（p < 0.05）。相比之下，单独使用E2以及E2与同时进行的高幅度GnRH刺激均使促卵泡生成素（FSH）的组织储存量降低（p < 0.05）。E2降低了FSHβ亚基的mRNA浓度（p < 0.05），但对α亚基或LHβ亚基的mRNA浓度没有影响。（摘要截断于250字）
