Galway A B, Lapolt P S, Tsafriri A, Dargan C M, Boime I, Hsueh A J
Department of Reproductive Medicine, University of California-San Diego, La Jolla 92093.
Endocrinology. 1990 Dec;127(6):3023-8. doi: 10.1210/endo-127-6-3023.
Ovulation in mammals is preceded by surges of the two pituitary gonadotropins, LH and FSH. Although previous studies have shown that purified FSH induces ovulation when administered to hypophysectomized rats, proof that FSH has inherent ovulatory potential is lacking because all FSH preparations have varying degrees of residual LH. To determine if FSH alone can induce ovulation, we generated LH-free recombinant FSH (RCFSH) by culturing eukaryotic cells transfected with the human common alpha- and FSH beta-subunit genes. Immature hypophysectomized rats were implanted with estrogen and then primed with PMSG (15 IU, sc). Fifty-two hours later, either RCFSH or hCG was injected (sc) to induce ovulation. A dose-dependent increase in the ovulation rate was stimulated by RCFSH, reaching 100% ovulation at 18 IU/rat, comparable to that achieved with 12 IU hCG. The maximum number of oocytes ovulated per ovary was similar for both groups. Ovulation induced by either RCFSH or hCG was time dependent and associated with a periovulatory increase in the ovarian activity and message levels of tissue-type plasminogen activator, a protease important in the preovulatory degradation of the follicle wall. Because PMSG has inherent LH-like activity in rats, we also implanted hypophysectomized rats with a minipump (sc) that released RCFSH (4 IU/day) to induce follicle growth. Fifty-two hours later, a single sc injection of a surge dose (20 IU) of RCFSH also induced ovulation, further indicating the ability of FSH alone to induce both follicle growth and ovulation. To test whether FSH can also induce ovulation in adult animals, rats were hypophysectomized on proestrous morning and treated with increasing doses of RCFSH (ip) to induce ovulation. At 7.8 IU RCFSH, all rats ovulated, with about 10 oocytes/rat. These results demonstrate that RCFSH is capable of inducing ovulation in hypophysectomized immature and adult rats, with associated increases in ovarian tissue-type plasminogen activator gene expression. Thus, FSH may be involved in follicular rupture in addition to its role in follicle recruitment and maturation. The preovulatory surges of both LH and FSH may represent a protective mechanism to ensure an optimal ovulatory stimulus. The present finding also serves as the basis to formulate new ovulation induction protocols.
哺乳动物排卵前会出现两种垂体促性腺激素（促黄体生成素和促卵泡生成素）的激增。尽管先前的研究表明，给垂体切除的大鼠注射纯化的促卵泡生成素可诱导排卵，但由于所有促卵泡生成素制剂都有不同程度的促黄体生成素残留，因此缺乏促卵泡生成素具有内在排卵潜力的证据。为了确定单独的促卵泡生成素是否能诱导排卵，我们通过培养转染了人类共同α亚基和促卵泡生成素β亚基基因的真核细胞，制备了无促黄体生成素的重组促卵泡生成素（RCFSH）。对未成熟的垂体切除大鼠植入雌激素，然后用孕马血清促性腺激素（15国际单位，皮下注射）进行预处理。52小时后，注射RCFSH或人绒毛膜促性腺激素（皮下注射）以诱导排卵。RCFSH刺激排卵率呈剂量依赖性增加，在18国际单位/只大鼠时排卵率达到100%，与12国际单位人绒毛膜促性腺激素的效果相当。两组卵巢排出的最大卵母细胞数量相似。RCFSH或人绒毛膜促性腺激素诱导的排卵具有时间依赖性，并且与排卵前卵巢组织型纤溶酶原激活物活性及信使水平的增加相关，组织型纤溶酶原激活物是一种在排卵前卵泡壁降解中起重要作用的蛋白酶。由于孕马血清促性腺激素在大鼠中具有内在的促黄体生成素样活性，我们还对垂体切除的大鼠皮下植入一个释放RCFSH（4国际单位/天）的微型泵以诱导卵泡生长。52小时后，单次皮下注射高剂量（20国际单位）的RCFSH也能诱导排卵，进一步表明单独的促卵泡生成素能够诱导卵泡生长和排卵。为了测试促卵泡生成素是否也能在成年动物中诱导排卵，在动情前期早晨对大鼠进行垂体切除，并用递增剂量的RCFSH（腹腔注射）诱导排卵。在7.8国际单位RCFSH时，所有大鼠都排卵，每只大鼠约有10个卵母细胞。这些结果表明，RCFSH能够在垂体切除的未成熟和成年大鼠中诱导排卵，并伴有卵巢组织型纤溶酶原激活物基因表达的增加。因此，促卵泡生成素除了在卵泡募集和成熟中发挥作用外，可能还参与卵泡破裂过程。促黄体生成素和促卵泡生成素的排卵前激增可能代表一种保护机制，以确保最佳的排卵刺激。目前的发现也为制定新的排卵诱导方案奠定了基础。
