Girmus R L, Wise M E
Department of Animal Science, University of Arizona, Tucson 85721.
Biol Reprod. 1991 Jul;45(1):128-34. doi: 10.1095/biolreprod45.1.128.
To determine the direct, chronic actions of progesterone (P4) and estrogen (estradiol, E2) on anterior pituitary synthesis and release of LH, 24 western range ewes underwent hypothalamic-pituitary disconnection (HPD) and ovariectomy (OVX) during the breeding season and were pulsed with exogenous GnRH with or without steroid replacement. Sequential blood samples were collected before infusion of GnRH and on Days 7 and 14 of GnRH infusion. Silastic capsules of P4 and/or E2 were implanted s.c. on Day 7 and remained in place throughout the experiment. Control ewes received only GnRH infusion. Blood sampling was centered around three exogenous GnRH pulses. After the final blood sampling, pituitaries were collected and stored at -70 degrees C. Concentrations of LH in serum and pituitaries were determined by RIA. Relative concentrations of LH subunit mRNAs were determined by Fast Blot analysis. Simultaneous implantation of P4 and E2 lowered LH pulse amplitude 70% and mean serum levels 30% compared with controls. Neither steroid alone affected LH release. E2 alone or in combination with P4 lowered LH-beta subunit mRNA concentrations 40% compared with controls while alpha-subunit levels were unchanged. Only E2 alone altered the pituitary content of LH, causing a 60% decrease. We conclude that the combination of P4 and E2 is necessary for inhibition of GnRH-stimulated LH secretion. E2 inhibits GnRH-stimulated LH-beta subunit mRNA concentrations but does not affect alpha-subunit mRNA concentrations. The control of pituitary LH content by P4 and E2 is the result of changes in both LH-beta subunit mRNA concentrations and LH secretion.
为了确定孕酮（P4）和雌激素（雌二醇，E2）对垂体前叶合成和释放促黄体生成素（LH）的直接慢性作用，在繁殖季节对24只西部牧场母羊进行下丘脑 - 垂体切断术（HPD）和卵巢切除术（OVX），并在有或无类固醇替代的情况下给予外源性促性腺激素释放激素（GnRH）脉冲。在输注GnRH之前以及输注GnRH的第7天和第14天采集序贯血样。在第7天皮下植入P4和/或E2的硅橡胶胶囊，并在整个实验过程中保留在位。对照母羊仅接受GnRH输注。采血围绕三个外源性GnRH脉冲进行。在最后一次采血后，收集垂体并储存在-70℃。通过放射免疫分析（RIA）测定血清和垂体中LH的浓度。通过快速印迹分析测定LH亚基mRNA的相对浓度。与对照组相比，同时植入P4和E2可使LH脉冲幅度降低70％，平均血清水平降低30％。单独使用任何一种类固醇均不影响LH释放。与对照组相比，单独使用E2或与P4联合使用可使LH-β亚基mRNA浓度降低40％，而α-亚基水平不变。仅单独使用E2改变了垂体中LH的含量，导致其降低了60％。我们得出结论，P4和E2的组合对于抑制GnRH刺激的LH分泌是必需的。E2抑制GnRH刺激的LH-β亚基mRNA浓度，但不影响α-亚基mRNA浓度。P4和E2对垂体LH含量的控制是LH-β亚基mRNA浓度和LH分泌变化的结果。
