Initiation of Asymmetrical Ovarian Estradiol Secretion in the Primate Ovarian Cycle after Luteectomy

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Abstract
We investigated the onset of asymmetrical ovarian function in rhesus monkeys after luteectomy, a procedure that has been shown to synchronize the initiation of new follicle growth. Monkeys underwent laparotomy for luteectomy 17–19 days after the spontaneous onset of menses. Subsequent laparotomy for ovarian inspection and ovarian venous blood collection was performed on days 1, 3, or 5 after luteectomy and on day 16 to determine the location of the new corpus luteum. Femoral blood was collected daily beginning 8 days after the onset of menses for the measurement of hormones. Luteectomy was followed by an abrupt decline in serum progesterone levels, the early onset of menses, and a prompt transient rise in FSH concentrations in all monkeys. The patterns of LH, FSH, 17β- estradiol, and progesterone in peripheral blood of monkeys that maintained ovulatory cycles, as indicated by midcycle type preovulatory gonadotropin surges 12.3 ±2.1 days after luteectomy, contained elevations of serum progesterone and an identifiable corpus luteum 16 days after the removal of luteal tissue. Uniformly, the ovary bearing the new ovulatory follicle was contralateral to the side of luteectomy. Despite removal of the corpus luteum, progesterone secretion (day 1) from the luteectomized ovary was transiently greater. This differential was not maintained 3 or 5 days after luteectomy. No asymmetry of ovarian venous 17β-estradiol levels was evident in ovulatory monkeys 1 or 3 days after luteectomy. In contrast, all ovulatory monkeys that provided ovarian venous blood 5 days after luteectomy manifested clear asymmetry of 17β-estradiol secretion (343 + 68 vs. 87 + 24 pg/ml). These observations indicate that the putative preovulatory (dominant) follicle is selected by about day 5 after the initiation of synchronous new follicle growth. Among anovulatory monkeys, symmetry in the secretion of 17β-estradiol was maintained, suggesting that recruitment and selection of a new dominant follicle did not occur.

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