Studies of the mechanism(s) of mammalian ovulation

Y. Yoshimura, E. E. Wallach

Research output: Contribution to journalReview articlepeer-review

Abstract

In most mammals, oocyte maturation and ovulation occur at predictable times and in a particular sequence after the gonadotropin surge. However, many local factors intervene between the preovulatory gonadotropin stimulus and ovulation. Experimental approaches using the in vitro perfused rabbit ovary provide important information regarding synchronization of follicle rupture and oocyte maturation. In this system, prostaglandins, norepinephrine, histamine, or streptokinase can induce follicle rupture but not oocyte maturation. These conditions presumably alter the apical region of the follicle wall through vascular, enzymatic, or inflammatory influences that facilitate follicle disruption and immature ovum discharge. Experimental methods that dissociate oocyte maturation and follicle rupture may provide interesting clues concerning the local intrafollicular cellular and molecular mechanisms regulating these processes. Gonadotropin-releasing hormone (GnRH) has recently been demonstrated to induce both ovulation and meiosis in hypophysectomized rats in the absence of gonadotropin. GnRH causes the ovulatory responses normally elicited by LH, including resumption of meiosis, dispersion and mucification of cumulus cells, elevation of plasma P, and ovulation. Furthermore, pretreatment in these experiments with a prostaglandin synthetase inhibitor completely inhibits GnRH-induced prostaglandin increase and ovulation, but not resumption of meiosis. The mechanism by which GnRH stimulates ovulation remains unclear, but GnRH-induced ovulation may be mediated by prostaglandins. The relative amounts of locally produced hormones, which act on the different components of the follicle simultaneously or in a particular sequence, appear to determine the maturational stage of the oocyte and cumulus differentiation during the process of ovulation.

Original languageEnglish (US)
Pages (from-to)22-34
Number of pages13
JournalFertility and sterility
Volume47
Issue number1
DOIs
StatePublished - 1987

ASJC Scopus subject areas

  • Reproductive Medicine
  • Obstetrics and Gynecology

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