In many nonprimate mammalian species, cyclical regression of the corpus luteum (luteolysis) is caused by the episodic pulsatile secretion of uterine PGF2α, which acts either locally on the corpus l...

Luteolysis: A Neuroendocrine-Mediated Event

Mice carrying a null mutation for either of the two cyclooxygenase (COX) isoenzymes, necessary for prostanoid production, exhibit several isotype-specific reproductive abnormalities. Mice deficient in COX-1 are fertile but have decreased pup viability, whereas mice deficient in COX-2 fail to ovulate and have abnormal implantation and decidualization responses. The present study identifies the specific contribution of each COX isoenzyme in hypothalamic, pituitary, and ovarian function and establishes the pathology and rescue of the anovulatory syndrome in the COX-2-deficient mouse. In both COX-1- and COX-2-deficient mice, pituitary gonadotropins were selectively increased, whereas hypothalamic LHRH and serum gonadotropin levels were similar to those in wild-type animals (+/+). No significant differences in serum estrogen or progesterone were noted among the three genotypes. Exogenous gonadotropin stimulation with PMSG and hCG produced a comparable 4-fold increase in ovarian PGE2 levels in wild-type and COX...

/pdf/anovulation-in-cyclooxygenase-2-deficient-mice-is-restored-2uc6fgeznl.pdf

Anovulation in cyclooxygenase-2-deficient mice is restored by prostaglandin E2 and interleukin-1beta.

Prostaglandins impact on ovarian, uterine, placental, and pituitary function to regulate reproduction in female livestock. They play important roles in ovulation, luteal function, maternal recognition of pregnancy, implantation, maintenance of gestation, microbial-induced abortion, parturition, postpartum uterine and ovarian infections, and resumption of postpartum ovarian cyclicity. Prostaglandins have both positive and negative effects on reproduction; they are used to synchronize oestrus, terminate pseudopregnancy in mares, induce parturition, and treat retained placenta, luteinized cysts, pyometra, and chronic endometritis. Improved therapeutic uses for prostaglandins will be developed when we understand better their involvement in implantation, maintenance of luteal function, and establishment and maintenance of pregnancy.

Prostaglandins and reproduction in female farm animals.

Hormone receptor control of pulsatile secretion of PGF2α from the ovine uterus during luteolysis and its abrogation in early pregnancy

Publisher Summary This chapter discusses the control of luteal function in domestic ruminant animals. It focuses on data regarding the regulation of receptors for luteinizing hormone (LH) and the characterization of two distinct types of steroidogenic luteal cells. The function of the corpus luteum in ruminants is regulated by a complex interaction of the secretions from at least two other endocrine organs. The adenohypophysis secretes LH, generally accepted as the primary luteotropic hormone in these species. The chapter suggests that the number of luteal receptors for LH—but not circulating concentrations of LH—is correlated with serum levels of progesterone throughout the estrous cycle of ewes. Down-regulation of LH receptors depends upon occupancy of the receptor, based on correlation between number of receptors occupied and number lost after administration of 1 mg of LH in vivo. The major pathway for loss of human chorionic gonadotropin (hCG) or LH bound to the luteal receptor for LH is via internalization and degradation of the hormone. Over 80% of 125I-labeled hCG bound to luteal cells in culture is internalized and degraded. A lesser amount of 125I-labeled LH is internalized and degraded because more of this hormone dissociates from the receptor. A major portion of the internalized population of receptors is recycled to the plasma membrane.

Regulation of luteal function in domestic ruminants: new concepts.

Utero-ovarian vein blood was collected via indwelling cannulae at 2-hr intervals from 6 conscious cycling ewes, either from the uterus in situ or from the autotransplanted uterus. Radioimmunoassays were used to analyze plasma samples for progesterone (P) estradiol-17β (E2-17β) luteinizing hormone (LH) and prostaglandin F2α (PGF2α-confirined by GLC/mass spec). Although peaks of E2-17β (12 to 42 pg/ml) occurred throughout the estrous cycle (including the day 3–4 peak) it was not until day 13 or 14 that peaks of PGF2α (3 to 8.5 ng/ml) were associated with E2-17β peaks (12 to 132 pg/ml). Larger peaks of PGF2 Q (9 to 23.0 ng/ml) lasting 2 hr or less, occurred on day 15 and were associated with the completion of luteal regression as evidenced by a fall in P cone. To determine whether the association of E2-17β peaks with PGF2α peaks was significant and also to determine whether the apparent effect of E2-17β on PGF2a release from the uterus was direct or indirect, a physiological amount of E2-17β (1.0 ng/min) was...

The Effect of Endogenous and Exogenous Estradiol-17β on the Release of Prostaglandin F2α from the Ovine Uterus

HORMONAL AND RELATED FACTORS AFFECTING THE RELEASE OF PROSTAGLANDIN F2α FROM THE UTERUS

/pdf/prostaglandin-f2a-and-the-release-of-lh-in-sheep-2sdfzujfw0.pdf

PROSTAGLANDIN F2α AND THE RELEASE OF LH IN SHEEP

The physiological role of prostaglandin F2alpha in corpus luteum regression.

Indomethacin, a known inhibitor of prostaglandin (PG) synthesis, blocked the estradiol-17β (E2-17β)-induced release of luteinizing hormone (LH) in sheep. This finding provides evidence of an obligatory role for endogenous PG synthesis in the mechanism of LH release. In addition it suggests a possible use for PG inhibitors in fertility control through the blockade of LH release and hence ovulation.

The blockade of LH release by indomethacin.

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