Sato N, Yanaihara T, Kanazawa M, Okinaga S, Arai K
Nihon Naibunpi Gakkai Zasshi. 1976 Aug 20;52(8):845-50. doi: 10.1507/endocrine1927.52.8_845.
The effects of the oral contraceptive on the pituitary content and plasma level of LH and the hypothalamic LH-RH level were investigated in 16 adult female rabbits. The oral contraceptive preparation, Sophia-C (Norethindrone 2mg + Mestranol 0.1 mg), as administered orally by a stomach tube each day for 7 days in 8 adult female rabbits. At the end of the treatment, the rabbits were bled from the abdominal aorta into heparinized syringes and the plasma was separated. The stalk median eminences were excised. All the materials were stored in -80 degrees C until assayed. Plasma level and the pituitary content of LH and the hypothalamic LH-RH were measured by radioimmunoassay. All the dose response curved were drawn using logitlog transformation. Radioimmunoassay procedures for LH was described in detail elsewhere. Purified rabbit LH for iodination (125-I) and strandard were prepared by T. Makino and R.O. Greep, at Research Laboratories for Human Reproduction, Harvard Medical School, Boston, U.S.A. The starting B/T was 25% at the final dilution of the antibody of 1/20,000. Minimal detectable quantity was about 40 pg/tube. The 50% intercepts were approximately 460 pg/tube. Radioimmunoassay procedures for LH-RH were performed according to the method described by Arimura et al. Antiserum against synthetic LH-RH was kindly supplied to us by Drs. A. Arimura and A.V. Schally, New Orleans, U'S.A. The synthetic LH-RH was kindly supplied to us by Dr. N. Yanaihara. The starting B/T ratio was 29% at the final dilution of the antibody of I/17,500. Minimal detectable quantity was about 40pg/tube and the 50% intercepts were 150pg/tube. It has been assumed that oral contraceptive drugs exert their action by blocking the hypothalamic LH-RH, resulting in a depression of the plasma level of LH, because plasma level of LH returned to the normal level when LH-RH was administered intravenously even while oral contraceptive steroids were given continuously. However, these findings concerning the site of action of the drugs furnished only indirect evidences. The possibility of a direct inhibitary effect of these steroids on the anterior pituitary cannot be ruled out. Administration of 2mg of Norethindrone and 0.1mg of Mestranol significantly depressed both the pituitary content and the plasma level of LH. On the other hand, they significantly increased the hypothalamic LH-RH level. Those findings strongly suggested the direct action of this drug on the anterior pituitary in the female adult rabbits. Detailed mechanisms on how the hypothalamic LH-RH was increased were not known in this experiment, further investigations are now in progress.
在16只成年雌性兔子身上研究了口服避孕药对垂体中促黄体生成素（LH）含量、血浆水平以及下丘脑促性腺激素释放激素（LH - RH）水平的影响。将口服避孕药制剂Sophia - C（炔诺酮2毫克 + 炔雌醇甲醚0.1毫克），通过胃管每天给8只成年雌性兔子口服，持续7天。治疗结束时，从腹主动脉将兔子放血至肝素化注射器中，分离出血浆。切除垂体柄正中隆起。所有材料均储存在 -80摄氏度直至检测。通过放射免疫分析法测定血浆中LH水平、垂体中LH含量以及下丘脑LH - RH水平。所有剂量反应曲线均采用logit - log转换绘制。LH的放射免疫分析程序在其他地方有详细描述。用于碘化（125 - I）的纯化兔LH和标准品由美国波士顿哈佛医学院人类生殖研究实验室的T. Makino和R.O. Greep制备。在抗体最终稀释度为1/20,000时，起始结合率（B/T）为25%。最小可检测量约为40皮克/管。50%截距约为460皮克/管。LH - RH的放射免疫分析程序按照有村等人描述的方法进行。抗合成LH - RH的抗血清由美国新奥尔良的有村博士和A.V. Schally博士惠赠。合成LH - RH由柳原博士惠赠。在抗体最终稀释度为1/17,500时，起始B/T比值为29%。最小可检测量约为40皮克/管，50%截距为150皮克/管。据推测，口服避孕药通过阻断下丘脑LH - RH发挥作用，导致LH血浆水平降低，因为即使持续给予口服避孕药类固醇，静脉注射LH - RH时LH血浆水平仍会恢复到正常水平。然而，这些关于药物作用部位的发现仅提供了间接证据。不能排除这些类固醇对垂体前叶有直接抑制作用的可能性。给予2毫克炔诺酮和0.1毫克炔雌醇甲醚显著降低了垂体中LH含量和血浆中LH水平。另一方面，它们显著提高了下丘脑LH - RH水平。这些发现强烈提示该药物对成年雌性兔子的垂体前叶有直接作用。在本实验中，下丘脑LH - RH升高的详细机制尚不清楚，目前正在进行进一步研究。
