Cellular mechanisms of luteolysis

Luteinizing granulosa cells synthesize high concentrations of progesterone, prostaglandin (PG) E 2 and PGF 2 . The objective of this study was to explore the relationship between prostaglandin and progesterone output from human granulosa cells as they undergo functional luteinization in culture. Granulosa cells were partially purified from ovarian follicular aspirates and cultured at a density of 10 5 cells/ml in serum-supplemented DMEM:Ham's F 12 medium for 0, 1 or 2 days. Cells were then switched to serum-free medium for 24 h before measuring hormone concentrations in this spent medium by specific radioimmunoassays. Over the first 3 days in culture, PGF 2 and PGE 2 production declined progressively by up to 82 3% coincident with a 55 11% increase in progesterone output. In subsequent experiments, cells were treated for 24 h on the second day of culture with either 0·01 to 10 µM meclofenamic acid or with 10 µM and 100 µM aminoglutethimide. Meclofenamic acid inhibited synthesis of PGF 2 and PGE 2 by up to 70 9% and 64 7% respectively without affecting progesterone output. Likewise, 100 µM aminoglutethimide inhibited progesterone production by 62 6% without affecting concentrations of either PGF 2 or PGE 2 . We have concluded that the progressive decline in prostaglandin production and the rise in progesterone output from luteinizing human granulosa cells occur independently of each other.

Section: Discussionmentioning

confidence: 99%

Relationship between the production of prostaglandins and progesterone by luteinizing human granulosa cells

Fowkes

Chandras²,

Chin³

et al. 2001

“…In particular, growth hormone (GH) ( Jia et al 1986, Sirotkin & Nitray 1994a, Sirotkin 1996a, insulin-like growth factor-I (IGF-I) (Giudice 1992, Paton & Collins 1992, Spicer & Echternkamp 1995, oxytocin (OT) (Wathes 1989, Sirotkin 1995, 1996b and prostaglandin (Dennfors et al 1983, Satoh et al 1984, Michael et al 1994 can regulate gonadotropin receptors, secretion of growth factors, steroid and nonapeptide hormones, prostaglandin F2-alpha (PGF) and cyclic nucleotides by rodent, bovine and human ovarian cells.…”

Section: Introductionmentioning

confidence: 99%

“…In pigs, effects of gonadotropin (Hillier 1991, Sirotkin & Nitray 1994b, Sirotkin et al 1994, Erickson 1995, Erickson & Danforth 1995, OT , Sirotkin 1995, 1996b and prostaglandin (Dodson & Watson 1979, Michael et al 1994) on ovarian secretions have been reported. On the other hand, there is very little information on the effects of GH and IGF-I on ovarian secretion in this species.…”

Section: Introductionmentioning

confidence: 99%

Isolated porcine ovarian follicles as a model for the study of hormone and growth factor action on ovarian secretory activity

Sirotkin

Makarevich²,

Kotwica³

et al. 1998

The aim of our in vitro experiments with isolated porcine ovarian follicles was to study the effects of gonadotropins, GH, IGF-I and oxytocin (OT) on release of ovarian steroid, OT, IGF-I, insulin-like growth factorbinding protein-3 (IGFBP-3), prostaglandin F (PGF), prostaglandin E (PGE) and cAMP.It was found that quarters of ovarian follicles cultured for 8 days produced significant amounts of progesterone, estradiol-17 beta, OT and IGFBP-3 with peaks of accumulation from the 3rd to the 8th day of culture. Addition of serum promoted progesterone, estradiol and OT release, whilst accumulation of IGFBP-3 was maintained to a greater extent in serum-free medium.GH (10 ng/ml or above) was able to inhibit androstenedione, OT, PGF and IGFBP-3, to stimulate IGF-I and cAMP, and to alter testosterone and PGE release by follicles cultured in serum-supplemented and/or serumfree medium. IGF-I (10 ng/ml or more) inhibited androstenedione and PGF secretion, stimulated testosterone, estradiol, OT and cAMP production, but did not influence progesterone, IGFBP-3 or PGE output in these conditions. OT (100 ng/ml) was able to inhibit androstenedione and to stimulate testosterone, IGF-I, PGF and PGE, but not estradiol or IGFBP-3 release. A stimulatory effect of LH on progesterone and OT and an inhibitory influence of LH on estradiol secretion in the serumsupplemented medium were observed. FSH in these conditions stimulated OT, but not progesterone or estradiol secretion.The use of this experimental model suggests the involvement of gonadotropins, OT, GH and IGF-I in the control of ovarian steroid and nonapeptide hormone, growth factor, growth factor-binding protein, prostaglandin and cyclic nucleotide production. The stimulatory effect of GH on IGF-I, and the stimulatory influence of IGF-I on OT, as well as coincidence of the majority of effects of IGF-I and OT, suggest the existence of a GH-IGF-I-OT axis. On the other hand, the different patterns of action of GH and IGF-I on OT, estrogen and IGFBP-3 suggest that part of the GH effect on ovarian cells is IGF-I independent.

“…Therefore, luteal function has been assumed to be regulated by interaction of luteotrophic and luteolytic PGs. On the basis of these results and the observation that the PGE 2 : PGF 2 synthesis ratio declined from the mid-to the late-luteal phase, induction of luteolysis in primates has been suggested to be actively initiated by endogenous PGF 2 (Challis et al 1976, Balmaceda et al 1980, Patwardhan & Lanthier 1980, Sargent et al 1988, Michael et al 1994.…”

Section: Introductionmentioning

confidence: 98%

“…It has been assumed that the antigonadotrophic mechanisms believed to underlie the luteolytic action of PGF 2 in vivo require a certain degree of luteal tissue integrity/ cell-cell contact, because stimulation of release of progesterone by PGF 2 can only be observed in a dispersed cell system (Auletta & Flint 1988, Michael et al 1994. In contrast, the action of PGE 2 is independent of cell-cell contact, consistently leading to stimulation of progesterone release in the different systems used .…”

Section: Introductionmentioning

confidence: 99%

Direct effects of the prostaglandins E2 and f2alpha on progesterone release by the corpus luteum of the marmoset monkey (Callithrix jacchus) studied by in vitro microdialysis

Fehrenbach

Hodges²,

Einspanier³

1999

The effects of the prostaglandins (PG) E 2 and F 2 on progesterone secretion in luteal tissue (32 corpora lutea) explanted from the mid-luteal ovary of the marmoset monkey (n=13) were investigated using an in vitro microdialysis system. Consecutive applications of 1, 10 and 100 µg/ml PGE 2 resulted in a significant increase in secretion of progesterone at the maximum dose of 100 µg/ml, which was shown to be the stimulatory dose in both long-period and 20-min pulse (time to collect one fraction) applications. The response varied individually between 1·4-and 3·4-fold above the baseline concentrations. Application of 500 µg/ml PGF 2 led to similar hormone responses. In contrast, lower doses of PGF 2 (0·5, 5 and 50 µg/ml) resulted in significantly increased levels of secretion of progesterone, to approximately 1·4-fold baseline values, only after the application was terminated (echo effect). Responses were less variable when a short pulse of 20 min duration was applied, instead of long applications of 1-2 h. On the basis of the passage rates measured for tritiated PGF 2 , transfer through the dialysis membrane was assumed to be in the range of 1% for both PGs. Ultrastructurally, luteal cells lying in a sheath of five to seven cell layers around the dialysis tubing appeared intact and were interconnected by gap junctions. Vesiculation of the smooth endoplasmic reticulum was more prominent after PG treatment, indicating a stimulation of cellular synthesis/secretory activities that was in accordance with the stimulatory action of both PGs on progesterone release under these in vitro conditions.