Stimulation of androstenedione and progesterone release by LHRH and LHRH agonist from isolated rat preovulatory follicles (original) (raw)
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Reproduction, 1982
Ewes were ovariectomized before (Group 1, N = 5) or after (Group 2, N = 6) the peak of the preovulatory gonadotrophin surge. Ovarian secretion rates of oestradiol and testosterone were significantly higher in Group 1 than in Group 2. The presence of high levels of LH receptors in both thecal and granulosa cells was used to identify ovulatory from non-ovulatory follicles. There was a significant fall in the LH receptor concentration in the thecal and granulosa cells of ovulatory follicles after the peak of the preovulatory gonadotrophin surge. Ovulatory follicles in Group 1 produced significantly more oestradiol and testosterone in vitro than did those in Group 2. In both groups ovulatory follicles secreted significantly more oestradiol in vitro than did non-ovulatory follicles. Follicular fluid oestradiol concentrations were similar in pattern to the in-vitro oestradiol secretion activity in ovulatory and non-ovulatory follicles. However, follicular fluid testosterone concentrations were significantly higher in non-ovulatory follicles than in ovulatory follicles. Incubation of follicles with 250 ng testosterone/ml did not significantly alter the in-vitro oestradiol secretion rate in any of the groups of follicles except for Group 2 non-ovulatory follicles in which oestradiol accumulation increased. The number of thecal and granulosa cell LH receptors was significantly correlated with follicular fluid oestradiol concentrations in ovulatory follicles and with in-vitro oestradiol production by Group 1 ovulatory follicles. It is suggested that the fall in oestradiol secretion rates, which occurs after the peak of the preovulatory gonadotrophin surge, may be due to a decrease of aromatase activity associated with a fall in the concentration of LH receptors and is not due to a lack of the oestrogen precursor testosterone. The elevated concentration of testosterone and low oestradiol concentrations in non-ovulatory follicles compared with ovulatory follicles are probably due to an inactive aromatase system, perhaps associated with the lack of granulosa cell LH receptors.
Endocrinology, 1963
oratory have demonstrated a luteinizing hormone (LH)-releasing action of crude hypothalamic extracts. This conclusion was based on the ability of these extracts to deplete ovarian ascorbic acid in immature rats pretreated with gonadotrophins (1). Since this test animal is highly sensitive to LH, the extract either released LH from the hypophysis of the test animals or contained LH itself as a contaminant. The activity in the extract was heat stable, whereas LH is quite heat labile, which supports the conclusion that LH release had occurred from the pituitaries of the test animals (2). Tests with other substances known to be present in the extract indicated that the activity could not be accounted for by these compounds and suggested that a specific LH-releasing factor (LH-RF) might be present in hypothalamic tissue (1).
Journal of Physiology and Biochemistry, 2010
Rat ovaries stimulated with human folliclestimulating hormone (hFSH) overexpress a factor that attenuates the LH surge in the rat: the putative gonadotropin surge-attenuating factor (GnSAF). A reduced gondadotrope progesterone receptor (PR) phosphorylation/activation is likely to be the main causative factor involved in GnSAF bioactivity on LH release. Besides, GnSAF reduces LH synthesis as well as LH secretion, and it is not known whether PR is involved in the inhibitory action of GnSAF on LH synthesis. Thus, the purpose of the present work was to evaluate the involvement of PR in the inhibitory effects of GnSAF on LH synthesis in cycling rats. To this end we used a specific radioimmunoassay and reverse transcription-polymerase chain reaction (RT-PCR) to study the effect on LH pituitary content and LHβ mRNA expression of PR occupancy with P (3 mg/0.2 ml oil in diestrus) on the inhibitory effects of hFSH (0, 0.1, 1, and 10 IU) in metestrus (day 2) and diestrus (day 3) on LH synthesis on proestrus in intact and on day 4 in day 2 ovariectomized (OVX) rats injected with 5 and 10 μg of estradiol benzoate (EB) on days 2 and 3, respectively. Results showed that (1) hFSH decreased pituitary LH content in intact, but not in OVX rats injected with EB, without affecting LHβ mRNA levels, and (2) PR occupancy with P annulled the inhibitory action of hFSH on pituitary LH content. These results indicate that PR is involved in ovarian GnSAF effect on LH content probably at a post-transcriptional level.
Journal of Endocrinology, 2007
Hyperstimulation of ovarian function with human FSH (hFSH) attenuates the preovulatory surge of LH. These experiments aimed at investigating the mechanism of ovarian-mediated FSH suppression of the progesterone (P4) receptor (PR)-dependent LH surge in the rat. Four-day cycling rats were injected with hFSH, oestradiol benzoate (EB) or vehicle during the dioestrous phase. On pro-oestrus, their pituitaries were studied for PR mRNA and protein expression. Additionally, pro-oestrous pituitaries were incubated in the presence of oestradiol-17β (E2), and primed with P4 and LH-releasing hormone (LHRH), with or without the antiprogestin RU486. After 1 h of incubation, pituitaries were either challenged or not challenged with LHRH. Measured basal and LHRH-stimulated LH secretions and LHRH self-priming were compared with those exhibited by incubated pituitaries on day 4 from ovariectomized (OVX) rats in metoestrus (day 2) injected with hFSH and/or EB on days 2 and 3. The results showed that: i...
Reproduction, 2009
Administration of human FSH (hFSH) to cyclic rats during the dioestrous phase attenuates progesterone receptor (PR)-dependent events of the preovulatory LH surge in pro-oestrus. The increased bioactivity of the putative ovarian gonadotropin surge inhibiting/attenuating factor induced by hFSH treatment is not associated with a decrease in PR protein expression, and the possibility of its association at a PR posttranslational effect has been raised. The present experiments aimed to analyse PR phosphorylation status in the gonadotrope of rats with impaired LH secretion induced by in vivo hFSH injection. Two experimental approaches were used. First, incubated pro-oestrous pituitaries from hFSH-injected cycling and oestrogen-treated ovariectomized (OVX) rats were used to analyze the effect of calyculin, an inhibitor of intracellular phosphatases, on PR-dependent LH release, which was measured in the incubation medium by RIA. Second, pituitaries taken from hFSH-injected intact cycling and OVX rats and later incubated with P or GNRH1 were used to assess the phosphorylation rate of gonadotrope. The latter was analysed in formalin-fixed, paraffin-embedded tissue sections by immunohistochemistry using a MAB that recognizes the phosphorylated (p) form of PR at Ser294. Calyculin reduced the ovary-mediated inhibition of hFSH in GNRH1-stimulated LH secretion. In addition, the immunohistochemical expression of pSer294 PR was significantly reduced after ovarian stimulation with hFSH in pituitaries from pro-oestrous rats incubated with P or GNRH1. Altogether, these results suggested that the ovarian-dependent inhibitory effect of FSH injection on the preovulatory LH secretion in the rat may involve an increase in dephosphorylation of PR.
Endocrinology, 2011
Ovarian hyperstimulation syndrome (OHSS) incidentally occurs in controlled ovarian stimulation protocols and is associated with human chorionic gonadotropin (hCG) administration. OHSS is caused by increased vascular permeability (VP) and thought to be mediated by hypersecretion of vascular endothelial growth factor (VEGF) by granulosa cells. Low molecular weight (LMW)-LH agonists have a similar mode of action but a shorter half-life compared with hCG, which could potentially lead to a clinical benefit in reducing the risk for OHSS in controlled ovarian stimulation protocols. The objective of this study is to investigate the role of an orally active LMW-LH agonist in OHSS induction compared with recombinant LH (rec-LH) and hCG. Immature rats were hyperstimulated with pregnant mare serum gonadotropin, and ovulation was induced by hCG, rec-LH or a LMW-LH agonist. The degree of VP was determined by Evans Blue in the abdominal cavity. Ovaries were weighed, and VEGF concentration in the ovary was determined. Pregnant mare serum gonadotropin stimulation followed by single-dose hCG or rec-LH resulted in clear enlargement of the ovaries and increased VP and VEGF levels. However, ovulation induction with a single dose of the LMW-LH agonist did not result in increased VP and VEGF levels, and even multiple dosing to mimic a longer exposure did not induce OHSS symptoms. In conclusion, we demonstrated that the oral LMW-LH agonist did not induce VP in rat, indicative for OHSS, possibly due to reduced VEGF production. If this is translatable to human, this could potentially represent a clinical benefit in reducing the risk for OHSS when using these compounds in controlled ovarian stimulation protocols. (Endocrinology 152: 4350-4357, 2011) L H is a heterodimeric glycoprotein that plays a pivotal role in ovulation. LH is produced and secreted by the pituitary and binds with high affinity and high specificity to the extracellular domain of the LH receptor (LH-R), which belongs to the G protein-coupled receptor (GPCR) superfamily. The LH-R is predominantly expressed in gonadal tissues like ovary and testis and at much lower levels in nongonadal tissues like oviduct, uterus, and blood vessels (1). At midcycle, the LH surge is responsible for oocyte maturation, cumulus expansion, luteinization, and finally, follicular rupture in the ovary. Binding of LH to the LH-R also stimulates the theca cells in the ovary and Leydig cells in the testis to produce testosterone, which in females can be converted into estradiol by aromatase in the granulosa cells. Human chorionic gonadotropin (hCG), which is produced during pregnancy to maintain the early stages of pregnancy, also binds to the LH-R (2). Human CG is used in assisted reproductive therapy (ART) for oocyte maturation and ovulation induction as well as for luteal sup
Mechanism of action of luteinizing hormone and follicle-stimulating hormone on the ovary in vitro
Metabolism, 1977
The mechanism of action of luteinizing folliculogenesis and follicular growth, hormone (LH) and follicle-stimulating hor-oocyte maturation, follicular rupture, and mone (FSH) upon various cell types of the corpus luteum maintenance and steroidomammalian ovary is reviewed. Emphasis genesis. The roles of gonadotropin reis placed upon in vitro studies using organ ceptors, AMP, prostaglandins, protein and cell culture as well as short-term in-kinase, and protein synthesis in these LH cubations. FSH and LH actions upon the and FSH actions are discussed. Intrafollowing ovarian functions are discussed: ovarian regulation of LH and FSH action steroidogenesis and metabolism of the is reviewed, including a discussion of the ovary as a whole and of the isolated possible roles of follicular fluid inhibitors follicle and its component cell types, the upon oocyte maturation and granulosa cell granulosa and thecal cells, as well as luteinization.
Animal Reproduction Science, 1997
A model designed to mimic the action of LH in preovulatory follicle development was evaluated. The model involved treatment of ewes with GnRHa (50 micrograms kg-1 24 h-1; GnRHa) at the time of luteal regression followed by exogenous LH administered as a series of bolus injections of varying frequency and amplitude. Ovarian responses to this regimen were compared to data derived from the same animals during a normal follicular phase. In experiment 1 four ewes with an autotransplanted ovary were treated with GnRHa followed by hourly LH (2.5 micrograms NIH-oLH-S25 i.v.) for 60 h at which time a further bolus of LH (25 micrograms i.v.) was given to mimic the LH surge. Plasma FSH profiles and the pattern and rate of secretion of oestradiol, inhibin, androstenedione and testosterone by the ovary in normal and GnRHa treated ewes were similar, but ovulation did not occur following the induced follicular phase. Experiment 2 examined the ability of a revised LH regimen to induce ovulation in normal intact ewes. Ewes (n = 11) were treated with GnRHa at the time of luteal regression followed by LH injections (1.25 micrograms i.v.) administered every 3 h for 12 h, every 2 h for the next 12 h and every hour for the following 36 h (3,2,1 regimen). After 60 h of LH injections the animals received an 8 h infusion of oLH (25 micrograms min-1) designed to mimic the pre-ovulatory LH surge. This treatment resulted in normal follicular phase patterns of LH and FSH and had no effect on the incidence (100%) or number (1.6 +/- 0.1) of ovulations when compared to a normal cycle (100% and 1.8 +/- 0.2). Experiment 3 examined the pattern of ovarian follicular development and hormone secretion stimulated by the 3,2,1 LH regimen in ewes with autotransplanted ovaries (n = 8). The LH regimen stimulated normal pre-ovulatory follicular development (normal 1.4 +/- 0.2; induced 1.6 +/- 0.2) and a normal pattern of ovarian oestradiol and androstenedione secretion. Pulse analysis showed, however, that baseline steroid secretion was lower in induced animals during the late follicular phase reflecting lower baseline LH at this stage. We conclude that administration of a GnRHa at the time of luteal regression in conjunction with frequent low amplitude pulses of exogenous LH induce follicular and hormonal patterns that closely mimic those observed following normal luteal regression and that this regimen represents a useful model to study the role of LH in the control of follicular selection.