Preovulatory LH Surge Research Articles

Evidence for the LH-releasing pathway of seminal plasma NGF in male camelids

In the female camelid, systemic administration of NGF induces a preovulatory LH surge that results in ovulation, but the effects of seminal NGF in the male are unknown. In the present study, we tested the hypothesis that the LH-releasing pathway of NGF is present in male camelids. In Experiment 1, male llamas and alpacas were treated with NGF or GnRH (n = 2 llamas and 3 alpacas) and blood samples were collected from 1 h before to 3 h after treatment. Plasma LH concentrations increased after treatment in a surge-like fashion in both GnRH- and NGF-treated groups, but concentrations reached a maximum 2.5 times higher and remained elevated for at least 2 h longer in the NGF-treated group (treatment-by-time interaction, P = 0.01). In Experiment 2, we evaluated the LH and testosterone response to NGF vs saline treatment (n = 3 llamas and 3 alpacas). The LH response to NGF was similar to that in Experiment 1, and plasma testosterone concentrations were higher in the NGF group than in the saline group at 2, 4 and 6 h after treatment (P < 0.05). Results support the hypothesis that the LH-releasing pathway for NGF exists in male South American camelids. The LH response to NGF sustained circulating testosterone concentrations in llamas, suggesting a moderate role of NGF in testosterone secretion.

A study on stress response and fertility parameters in phenotypically thermotolerant and thermosensitive dairy cows during summer heat stress.

It is well documented that heat stress (HS) causes subfertility in dairy cows. However, during the last ten years we have been observing that, under high temperature-humidity index (THI≥75), despite the overall reduced fertility, some cows conceive at the first artificial insemination (AI). Here, we examined distinctive features of cows with conserved fertility under severe HS. From the databases of three herds, 167 lactating Holstein cows were selected; group TT cows (n=57) conceived in the previous summer (THI≥75) at the 1st AI, and group TS (n=110) failed to conceive at the same period after at least 2 consecutive AIs. The animals calved in spring, and in August, blood samples were collected during a hot day (THI≥81) for the determination of cortisol and HSP70 concentrations. In one farm, the validity of fertility data of the previous year was re-examined. In 28 cows from group TT and in 39 cows from group TS, the conception rate was examined during July and August. In 6 cows from each group (TT and TS) the oestrous cycles were synchronized, ovulation was induced with GnRH (THI=80), and the concentration of the pre-ovulatory LH surge was determined in 9 blood samples. The progesterone concentration in the ensuing cycle was determined in blood samples collected every other day. Overall, cortisol and HSP70 were significantly lower in TT group compared to TS. More (p<.05) animals from group TT conceived at the first AI compared with those from group TS. The induced pre-ovulatory LH surge peaked at higher level (p<.002) in group TT than in group TS, while no difference was recorded among groups either in mean progesterone concentrations or in the duration of the ensuing oestrous cycle. These results are highly suggestive that thermotolerance in some dairy cows is an inherent characteristic, warranting further genetic investigation.

Association between LH receptor regulation and ovarian hyperstimulation syndrome in a rodent model.

Ovarian hyperstimulation syndrome (OHSS) is a common complication of ovarian stimulation associated with the administration of human chorionic gonadotropin (hCG) during assisted reproduction. We have determined the expression of luteinizing hormone receptor (Lhcgr) mRNA, vascular endothelial growth factor (VEGF), and its transcription factor, HIF1α, during the periovulatory period in a rodent model of OHSS and compared these results with normal ovulatory periods. These results showed that the downregulation of Lhcgr mRNA in response to conditions that mimic preovulatory LH surge was significantly impaired in the OHSS group compared to the complete downregulation seen in the control group. Most importantly, the downregulation of luteinizing hormone receptor mRNA expression following hCG administration was sustained in the control group up to 48 h, whereas it remained at significantly higher levels in the OHSS group. This impairment of hCG-induced Lhcgr downregulation in the OHSS group was accompanied by significantly elevated levels of VEGF and its transcription factor, HIF1α. Furthermore, the downregulation of Lhcgr that occurs in response to a preovulatory LH surge in normal cycles was accompanied by low levels of VEGF. This study shows that, while downregulation of Lhcgr as well as low VEGF levels are seen in response to a preovulatory LH surge in normal ovarian cycle, impaired Lhcgr downregulation and elevated VEGF levels were found in the OHSS group.

Ovarian Dynamics, Plasma Endocrine Profile and Fertility Response Following Synchronization Protocols in Crossbred Cows with Cystic Ovaries

Background: Cystic ovarian degeneration (COD) with prevalence of 10-13% is a common and economically important condition in dairy cattle affecting fertility. Predisposing factors and aetiology of ovarian cysts are multifaceted. The most widely accepted cause is either absent, insufficient or wrong time occurrence of pre-ovulatory LH-surge. The accuracy of differential diagnosis of cyst per rectum can be increased by simultaneous use of USG and/or plasma progesterone assay and therapeutic success depends on type and duration of cystic condition. The literature on these aspects in crossbred cows is meagre, hence was planned to differentially diagnose the ovarian follicular and luteal cysts based on clinical, sonographic and endocrine findings and to study the estrus response and conception rates following different treatment modalities of COD in crossbred cattle. Methods: This study was conducted on greater than 90 days postpartum HF crossbred cows with cystic ovaries (n=58) confirmed by per rectal palpation and ultrasonography. The animals with follicular cysts were randomly treated with either conventional Ovsynch or Ovsynch + CIDR protocol (n=10 each) and those with luteal cysts with either Double PG injections 11 days apart or modified Ovsynch protocol (n=16 each) with fixed time AI. A group of six cystic cows was kept as untreated control. Blood samples were collected in heparinized vacutainers, together with trans-rectal ultrasonography, on day 0 (just before initiation of treatment), on day of last PGF2á injection, on day of induced estrus/FTAI and on day 12 post-AI for determination of plasma progesterone and estradiol-17â by RIA technique. Results: The mean diameters and wall thickness of ovarian cysts regressed significantly (p less than 0.01) among responded cows of all four protocols. The estrus induction response within 48-96 hrs of last PG injection with Ovsynch, Ovsynch + CIDR, Modified Ovsynch and Double PG protocols was 90.00, 100.00, 87.50 and 81.25 %, respectively. The conception rates at induced estrus with FTAI for these protocols were 50.00, 40.00, 50.00 and 43.75 %, respectively and the corresponding overall conception rates for 3 cycles’ post-treatment were 60.00, 70.00, 68.75 and 56.25 %, respectively, compared to zero result of control group. The mean plasma progesterone concentration varied highly significantly (p less than 0.01) between periods of treatment in all protocols, the values were lower (p less than 0.01) on day 0 and on day of FTAI than on the day of last PG injection and on day 12 post-AI. The values on day 12 post-AI were significantly higher in conceived than non-conceived cows. The trend of estradiol-17â profile on day of last PG injection was reversed than on day 0. The higher levels of estradiol-17â on day of FTAI were associated with regression of cystic structures and development of new dominant follicles with estrogenic activity concomitant to induced estrus and ovulatory LH surge in most of the animals as evident from USG monitoring, behavioural signs and conception rates.

Morphological and functional evidence for sexual dimorphism in neurokinin B signalling in the retrochiasmatic area of sheep.

Neurokinin B (NKB) is critical for fertility in humans and stimulates gonadotrophin-releasing hormone/luteinising hormone (LH) secretion in several species, including sheep. There is increasing evidence that the actions of NKB in the retrochiasmatic area (RCh) contribute to the induction of the preovulatory LH surge in sheep. In the present study, we determined whether there are sex differences in the response to RCh administration of senktide, an agonist to the NKB receptor (neurokinin receptor-3 [NK3R]), and in NKB and NK3R expression in the RCh of sheep. To normalise endogenous hormone concentrations, animals were gonadectomised and given implants to mimic the pattern of ovarian steroids seen in the oestrous cycle. In females, senktide microimplants in the RCh produced an increase in LH concentrations that lasted for at least 8hours after the start of treatment, whereas a much shorter increment (approximately 2hours) was seen in males. We next collected tissue from gonadectomised lambs 18hours after the insertion of oestradiol implants that produce an LH surge in female, but not male, sheep for immunohistochemical analysis of NKB and NK3R expression. As expected, there were more NKB-containing neurones in the arcuate nucleus of females than males. Interestingly, there was a similar sexual dimorphism in NK3R-containing neurones in the RCh, NKB-containing close contacts onto these RCh NK3R neurones, and overall NKB-positive fibres in this region. These data demonstrate that there are both functional and morphological sex differences in NKB-NK3R signalling in the RCh and raise the possibility that this dimorphism contributes to the sex-dependent ability of oestradiol to induce an LH surge in female sheep.

SAT-019 The Associations of Kisspeptin with Reproductive Hormones and Oocyte Maturation in Infertile Patients Who Underwent IVF Treatment

Kisspeptin has been recognized as a stimulatory factor of the hypothalamic-pituitary-gonadal (HPG) axis. Kisspeptin has been successfully used to trigger ovulation in in vitro fertilization (IVF) treatment (1). This study aimed to 1)compare reproductive hormones (FSH, LH, estradiol, progesterone, and AMH), serum and follicular fluid kisspeptin between successful and unsuccessful clinical pregnancy in different stages of IVF treatment; 2) determine the correlations of serum or follicular fluid kisspeptin with reproductive hormones as well as biochemical and clinical outcomes; and 3) compare the levels of kisspeptin between serum and follicular fluid. In this study, 30 infertile female patients (age 26–40 years old) undergoing IVF treatment were recruited. Blood samples were collected at 3 different time points, the beginning of gonadotropin stimulation (the early follicular phase or T1), the scheduled day for ovum pick-up (OPU) (the late follicular phase or T2), and the day of OPU (T3). Meanwhile, biochemical and clinical parameters including the number of retrieved oocytes, matured oocytes, 2 pronuclear (2PN), and serum hCG were also determined. Moreover, fetus heart beat at 6 weeks of gestation was measured to classify the subjects into successful (n=10) and unsuccessful (n=20) clinical pregnancies. Serum AMH at T1 was significantly higher but serum FSH at T1 and T2 was significantly lower in the success group compared with the unsuccess group (P<0.05 all). Serum kisspeptin at T2 (P=0.09) and serum estradiol at T3 (P=0.05) tended to be higher in the success group compared with non-success group. Serum kisspeptin at T1 had negative correlations with the number of retrieved oocytes (R=-0.511), matured oocytes (R=-0.388), and 2PN (R=-0.451) (P<0.05 all). Serum kisspeptin at T2 had positive correlations with serum LH at T2 (R=0.455), serum kisspeptin at T3 (R=0.645), the number of retrieved oocytes (R=0.465), matured oocytes (R=0.432), and 2PN (R=0.445), and serum hCG levels (R=0.438) (P<0.05 all). Serum kisspeptin at T3 had positive correlations with serum estradiol at T3 (R=0.380), the number of retrieved oocytes (R=0.601), matured oocytes (R=0.565), and 2PN (R=0.562) (P<0.05 all). Follicular fluid kisspeptin levels had a negative correlation with serum FSH at T3 (R=-0.482) but a positive correlation with the number of matured oocytes (R=0.407) (P<0.05 all). Kisspeptin levels in the follicular fluid (3.34 ± 3.74 ng/ml) were significantly higher than in serum at T3 (0.51 ± 0.13 ng/ml) (P<0.01). As a result, kisspeptin at T2 was positively correlated with LH and clinical outcomes, suggesting that kisspeptin might play a role in augmentation of pre-ovulatory LH surge, improvement of oocyte maturation, and ovulation.Thus, kisspeptin might be used as a potential predictor of successful IVF treatment. Reference: (1) Abbara A, et al. J Clin Endocrinol Metab. 2015;100(9):3322–31.

Persistent vs transient alteration of folliculogenesis and estrous cycle after neonatal vs adult exposure to Bisphenol A

Exposure to bisphenol A (BPA), a ubiquitous endocrine-disrupting chemical (EDC), is known to produce variable effects on female puberty and ovulation. This variability of effects is possibly due to differences in dose and period of exposure. Little is known about the effects of adult exposure to environmentally relevant doses of this EDC and the differences in effect after neonatal exposure. This study sought to compare the effects of neonatal vs adult exposure to a very low dose or a high dose of BPA for 2 weeks on ovulation and folliculogenesis and to explore the hypothalamic mechanisms involved in such disruption by BPA. One-day-old and 90-day-old female rats received daily subcutaneous injections of corn oil (vehicle) or BPA (25 ng/kg/d or 5 mg/kg/d) for 15 days. Neonatal exposure to both BPA doses significantly disrupted the estrous cycle and induced a decrease in primordial follicles. Effects on estrous cyclicity and folliculogenesis persisted into adulthood, consistent with a disruption of organizational mechanisms. During adult exposure, both doses caused a reversible decrease in antral follicles and corpora lutea. A reversible disruption of the estrous cycle associated with a delay and a decrease in the amplitude of the LH surge was also observed. Alterations of the hypothalamic expression of the clock gene Per1 and the reproductive peptide phoenixin indicated a disruption of the hypothalamic control of the preovulatory LH surge by BPA.

Genetic Deletion of Esr1 in the Mouse Preoptic Area Disrupts the LH Surge and Estrous Cyclicity.

Estrogen receptor α (ESR1) is critical for the generation of the preovulatory LH surge. Experiments in rodents have indicated a role for neurons located in the anteroventral periventricular area and preoptic periventricular nucleus [termed the rostral periventricular area of the third ventricle (RP3V)] in surge generation. In the current study, we aimed to examine whether ESR1 expressed by RP3V neurons was necessary for the LH surge. The estrous cycles of mice with estrogen receptor α (Esr1) exon 3 flanked by LoxP sites (Esr1 flox) and controls were monitored before and after bilateral stereotactic injection of adeno-associated virus encoding Cre recombinase into the RP3V. This resulted in 84% and 72% decreases in ESR1-immunoreactive cell numbers in the anteroventral periventricular area and preoptic periventricular nucleus, respectively, with no changes in the arcuate nucleus. Beginning three weeks after the adeno-associated virus injection, Esr1 flox mice began to show a loss of estrous cyclicity going, primarily, into constant estrus. Wild-type mice and Esr1 flox mice with injections outside the RP3V or unilateral ablations of ESR1 continued to exhibit normal estrous cycles. Mice were then gonadectomized and given an estradiol replacement regimen to generate the LH surge. This resulted in an absence of cFOS expression in GnRH neurons (1 ± 1% vs 28 ± 4% of GnRH neurons; P < 0.01) and markedly reduced LH surge levels (2.5 ± 0.6 vs 9.1 ± 1.0 ng/mL; P < 0.01) in Esr1 flox mice compared with controls. These results demonstrate that neurons expressing ESR1 within the RP3V are critical for the generation of the LH surge and estrous cyclicity in the mouse.

Evaluation of different hormonal treatments on oestral and ovarian responses in Moroccan Beni Arouss goats during anoestrus and breeding season.

The efficacy of eight combinations of fluorogestone acetate (FGA, 20 or 40mg as intravaginal device during 11days), equine chorionic gonadotropin (eCG, 300 or 500UI injected 48hr before FGA removal) and prostaglandin F2α (cloprostenol, 0 or 50μg injected 48hr before FGA removal) aiming at induction and synchronization of oestrus and ovulation was evaluated during the anoestrus season in spring and during the breeding season in autumn in adult Beni Arouss goats. Oestrous behaviour was recorded between 12 and 60hr after FGA removal. Blood samplings allowing to assess onset of the pre-ovulatory LH surge and increase of progesterone as sign of an active corpus luteum were performed, respectively, between 20 and 60hr and 3, 5, 8 and 15days after FGA removal. No season-related differences (spring vs. autumn) were observed for oestrous response (95% vs. 93%), pre-ovulatory LH surge (94% vs. 84%) and luteal response after 3-8 and 11-15days post-treatment (respectively 92% vs. 66% and 92% vs. 98%). The onset of oestrus (21 [13-53] vs. 32 [12-54]hr) and LH surge (26 [20-60] vs. 38 [22-60]hr) occurred significantly later in autumn. FGA (40 vs. 20mg) in autumn significantly delayed the onset of oestrus (36 [16-54] vs. 23 [12-47]hr) and LH surge (44 [26-58] vs. 33 [22-60]hr). Significant treatment-related differences were recorded for onset of LH surge (earliest for 20mg FGA, 300IU eCG, 50μg PGF2α ) and onset of luteal phase (latest for 40mg FGA, 300IU eCG, 50μg PGF2α ). In conclusion, the hormone combinations tested appeared equally effective in terms of oestrous and ovulation rates. Season has influenced significantly the onset of oestrus and LH surge, and the high dose regimen of FGA delayed the ovarian response in autumn.

C-type natriuretic peptide signaling in human follicular environment and its relation with oocyte maturation

Studies in mice have shown that C-type natriuretic peptide (CNP) is produced by granulosa cells and contributes to ovarian follicle growth and oocyte meiotic arrest until the preovulatory LH surge. In humans, the relationship between intraovarian CNP levels and oocyte meiotic resumption is unknown. The aim of this study was to investigate whether CNP and its receptor NPR2 are expressed in human ovarian follicles and if their levels change according to the meiotic phase of oocytes. We collected follicular fluid (FF) and luteinized granulosa cells (LGC) from follicle pools (n = 47), and FF, LGC and cumulus cells (CC) from individual follicles (n = 96) during oocyte pickup for in vitro fertilization. There was a positive linear correlation between CNP levels in FF pools and basal antral follicle counting (rs = 0.458; p = 0.002), number of preovulatory follicles >16 mm (rs = 0.361; p = 0.016) and number of oocytes retrieved (rs = 0,378; p = 0.011) and a negative correlation between CNP levels in FF pools and the percentage of mature (MII) oocytes retrieved (rs = −0.39; p = 0.033). FF CNP levels in follicles containing MII oocytes were significantly lower than in follicles containing immature (MI) oocytes (median = 0.44 vs. 0.57 ng/mL, p < 0.05). Accordingly, the CNP precursor gene NPPC was 50% less expressed in LGC from follicles containing MII oocytes than in follicles containing MI oocytes (p < 0.01). In addition, NPR2 mRNA was down-regulated in CC surrounding MII oocytes (60% reduction, p < 0.01). CNP signaling is downregulated in human ovarian follicles containing mature oocytes. Further studies should clarify whether CNP signaling is essential to keep oocyte meiotic arrest in humans.

SAT-423 The Involvement of GnRH Neurons in Mediating the Effects of RFRP-3 on the Mouse Reproductive Axis

In 2000, gonadotrophin-inhibitory hormone was discovered in birds and shown to inhibit gonadotrophin secretion. The mammalian ortholog was concurrently discovered in humans and rats and termed RFamide-related peptide-3 (RFRP-3). Recent results have shown that the effects of centrally-administered RFRP-3 on gonadotrophin secretion are sex- and cycle stage-dependent in mice (Ancel et al., 2017). Indeed, intracerebroventricular injections of RFRP-3 stimulated LH secretion in males, and inhibited LH secretion in females at the time of the preovulatory LH surge. In addition, the stimulatory effect observed in males was shown to be mediated in part by GPR54, the receptor for Kisspeptins, suggesting the involvement of other pathways. In order to further our understanding of the ways in which RFRP neurons modulate the reproductive axis, we have developed a novel transgenic mouse line. Using a Cre-loxP conditional transgenic method, we knocked the receptor for RFRP-3 (GPR147) out of GnRH neurons and analysed puberty onset in these mice. While the absence of GPR147 on GnRH neurons advanced puberty onset in male mice, it resulted in a delay in female puberty, once again indicating a sex-specific role of the RFRP system in the regulation of the reproductive function. Current work is aimed at dissecting the potential involvement of GnRH neurons in the pathways mediating RFRP-3 effects on LH secretion in mice carrying a deletion of GPR147 in GnRH neurons. Both male and female mice received intracerebroventricular injections of RFRP-3 and LH levels were subsequently assayed in tail-tip blood samples. This work is still ongoing. Taken together, these new tools provide us with the possibility to advance our understanding of the structure and the functions of the RFRP neuronal system in mice.

SAT-LB070 Tachykinins Are Essential for the Induction of the Preovulatory LH Surge in Mice

Tachykinins (TACs) result from the differential processing of two genes in rodents, Tac1 (encoding substance P (SP) and neurokinin A (NKA)) and Tac2 (encoding NKB). TACs exert their effects in the hypothalamus by acting on different G protein-coupled receptors (GPCRs): NK1R, the receptor of SP, NK2R, the receptor of NKA, and NK3R, the receptor of NKB. We and others have documented a stimulatory role for all these tachykinins in the release of GnRH in the presence of physiological circulating levels of sex steroids. Important cross-reactivity between the TAC ligand-receptor systems has been documented and suggested as a possible cause for the reversal of hypogonadal NKB-signaling deficient patients. In order to test the possible redundancy in the TAC systems, we generated a mouse model of congenital removal of all TACs (Tac1KO/Tac2KO, aka TACKO). This model revealed a sexually dimorphic effect of TACs on puberty onset and fertility. TACKO male mice (n= 14) displayed delayed puberty onset compared with wildtype (WT) littermates, resembling Tac1KO and Tac2KO mice separately, but retained normal fertility. By contrast, TACKO females presented a slight delay in the timing of vaginal opening (VO) -a marker of puberty onset—, compared to controls, but none of the females (n=10) presented signs of first estrus within 30 days after VO, indicating a failure to undergo complete sexual maturation. This was supported by a profound reproductive impairment, as only 20% of the TACKO females that were mated with fertile WT males for 8 weeks delivered pups (and these litters presented a significantly reduced number of pups and significantly larger parturition latency than controls). To test the ability of TACKO females to mount a normal LH surge, a similar cohort of TACKO females (n = 5) was subjected to an LH surge inducing protocol, which evidenced the absence of a detectable preovulatory surge in KO mice. Overall, these data suggest a novel role for TACs as essential players in the induction of the preovulatory LH surge in females, through a redundant mechanism that is only evident in the absence of all TACs, but not in the absence of Tac1 or Tac2, separately. These data further suggest that while TACs participate in the timing of puberty onset in both sexes, they are dispensable for the tonic (pulsatile) release of GnRH/LH as evidenced by the normal fertile phenotype of male TACKO mice. Because preoptic area Kiss1 neurons do not coexpress TACs, these findings strongly support an additional role for caudal hypothalamic (arcuate and ventromedial nuclei) neurons in the control of ovulation. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. s presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

The differential secretion of FSH and LH: regulation through genes, feedback and packaging

While the role of oestradiol and progesterone in the control of GnRH pulsatile secretion and generation of the preovulatory GnRH surge to induce release of the LH surge has been fully investigated, less attention has been given to changes in the pituitary gland that may sensitize gonadotrophs to switch from pulsatile release to surge release of LH, in particular. Furthermore, in the follicular phase while pulsatile secretion of LH is maximal, FSH secretion is reduced, yet both hormones are produced by the same gonadotrophs. The mechanisms whereby this differential release can occur are still unclear. The main regulator of FSH secretion is through the negative feedback effects of oestradiol and inhibin, which directly affect FSHbeta mRNA content and subsequent synthesis of FSH. FSH is then released predominantly via a constitutive pathway and the amount released is closely related to the rate of synthesis. In contrast, while basal LH secretion occurs via a constitutive pathway, the principal release of LH through pulsatile secretion is through the regulated pathway with GnRH stimulating the release of pre-synthesized LH contained in storage granules without significant changes in LHbeta mRNA. Secretogranin II (SgII) is associated with LH in these electron-dense storage granules and LH-SgII granules appear to be the principal form of granule released in response to GnRH through the regulated pathway. At the time of the preovulatory LH surge, granule movement to the gonadotrope cell membrane abutting a capillary, polarization, appears to play an important part in the priming mechanism for release of LH during the preovulatory LH surge in response to the GnRH surge. As there appears to be limited or no gonadotroph cell division in the adult pituitary gland, each gonadotroph passes through this synthesis and secretion pathway repeatedly through successive oestrous cycles. Packaging of LH and FSH into different secretory granules within the same cell is thus pivotal for the differential secretion of these gonadotrophins.

How does nutrition influence luteal function and early embryo survival

The pre-ovulatory LH surge triggers luteinisation of follicle tissue, but subsequent development of corpora lutea to full size is independent of LH up to around day 12 of pregnancy. Thereafter, severe (pharmacological) inhibition of LH secretion for 3 to 5 days will result in luteal failure and loss of pregnancy. It is unlikely that nutritional circumstances will have a similar effect, although scenarios with severe undernutrition have hardly been studied during early pregnancy. Milder levels of pre- and postmating undernutrition (around maintenance requirements), do affect luteal tissue development, but whether this is related to variation in LH is not clear as studies are equivocal, and there are indications that other nutrition related factors, like IGF-1 and insulin, may mediate these effects. A high plane of nutrition seems to increase progesterone secretion by the ovaries, even though systemic progesterone is reduced at the same time. Since there is direct transfer of progesterone from ovarian veins to the uterus, this may explain why a high plane of nutrition may actually benefit embryo survival and pregnancy, although very early during luteal formation (first days after mating), secretion by the ovaries may be overridden by systemic clearance of progesterone on a high feed level. Direct measurement of progesterone secretion by the ovaries is poorly understood as is the transfer of progesterone to the uterus and effects of specific nutrition related mediators such as IGF-1 and insulin on these processes.

The Contribution of the Circadian Gene Bmal1 to Female Fertility and the Generation of the Preovulatory Luteinizing Hormone Surge.

In rodents, the preovulatory LH surge is temporally gated, but the timing cue is unknown. Estrogen primes neurons in the anteroventral periventricular nucleus (AVPV) to secrete kisspeptin, which potently activates GnRH neurons to release GnRH, eliciting a surge of LH to induce ovulation. Deletion of the circadian clock gene Bmal1 results in infertility. Previous studies have found that Bmal1 knockout (KO) females do not display an LH surge at any time of day. We sought to determine whether neuroendocrine disruption contributes to the absence of the LH surge. Because Kiss1 expression in the AVPV is critical for regulating ovulation, we hypothesized that this population is disrupted in Bmal1 KO females. However, we found an appropriate rise in AVPV Kiss1 and Fos mRNA at the time of lights out in ovariectomized estrogen-treated animals, despite the absence of a measureable increase in LH. Furthermore, Bmal1 KO females have significantly increased LH response to kiss-10 administration, although the LH response to GnRH was unchanged. We then created Kiss1- and GnRH-specific Bmal1 KO mice to examine whether Bmal1 expression is necessary within either kisspeptin or GnRH neurons. We detected no significant differences in any measured reproductive parameter. Our results indicate that disruption of the hypothalamic regulation of fertility in the Bmal1 KO females is not dependent on endogenous clocks within either the GnRH or kisspeptin neurons.

New insights of the role of β-NGF in the ovulation mechanism of induced ovulating species.

The type of stimuli triggering GnRH secretion has been used to classify mammalian species into two categories: spontaneous or induced ovulators. In the former, ovarian steroids produced by a mature follicle elicit the release of GnRH from the hypothalamus, but in the latter, GnRH secretion requires coital stimulation. However, the mechanism responsible for eliciting the preovulatory LH surge in induced ovulators is still not well understood and seems to vary among species. The main goal of this review is to offer new information regarding the mechanism that regulates coitus-induced ovulation. Analysis of several studies documenting the discovery of β-NGF in seminal plasma and its role in the control of ovulation in the llama and rabbit will be described. We also propose a working hypothesis regarding the sites of action of β-NGF in the llama hypothalamus. Finally, we described the presence of β-NGF in the semen of species categorized as spontaneous ovulators, mainly cattle, and its potential role in ovarian function. The discovery of this seminal molecule and its ovulatory effect in induced ovulators challenges previous concepts about the neuroendocrinology of reflex ovulation and has provided a new opportunity to examine the mechanism(s) involved in the cascade of events leading to ovulation. The presence of the factor in the semen of induced as well as spontaneous ovulators highlights the importance of understanding its signaling pathways and mechanism of action and may have broad implications in mammalian fertility.

Onset of estrus and preovulatory LH surge and ovulatory efficiency in sheep after short-term treatments with progestagen-sponges and progesterone-CIDRs.

The present study supports that short-term (7-days) protocols based on progestagen-impregnated sponges and progesterone-loaded CIDRs are equally effective to induce ovulatory response in sheep. There were no significant differences in the onset of estrus behavior (32.0±6.0 and 33.8±4.0hr after device withdrawal for sponges and CIDRs, respectively; p>0.05) and preovulatory LH discharge (5.1±2.1 and 5.8±3.3hr after onset of estrus behavior for sponges and CIDRs, respectively; p>0.05). These features are similar to previously described for classical long-term (12-14days) treatments. Hence, short-term CIDR-based protocols may be implemented using the same time-intervals for insemination than sponge-based and long-term protocols.

Effects of short-term intravaginal progestagens on the onset and features of estrus, preovulatory LH surge and ovulation in sheep

In the present study, there was a comparison among classical long-term progestagen (fluorogestone acetate) protocols for synchronization of estrus and ovulation (14 days; group FGA14, n = 9 ewes) and short-term protocols based on 7 days of progestagen treatment plus a dose of prostaglandin F2α at either insertion (PG-FGA7, n = 11) or removal (FGA7-PG, n = 12). There were no significant differences in the ovulation rate and progesterone secretion among treatments. The FGA7-PG group, however, had a similar percentage of ewes expressing estrous behavior than the group FGA14 (90.9 and 100%, respectively, with a trend for a lesser percentage in the PG-FGA7 group, 63.6%) and about 90% of the ewes in the FGA7-PG group had the preovulatory surge release of LH 8 h after the onset of estrous behavior. These features may be related to a greater number of preovulatory follicles during growing phases (P < 0.05) and a greater plasma estradiol concentration (P < 0.05) in this group than in the classical 14-day group, which suggest these are more functional preovulatory follicles. In conclusion, therefore, the use of the FGA7-PG treatment may favor efficiency of progestagen-based protocols for reproductive management.

Regulation of LH secretion by RFRP-3 - From the hypothalamus to the pituitary.

RFamide-related peptides (RFRPs) have long been identified as inhibitors of the hypothalamus-pituitary-gonad axis in mammals. However, less progress has been made in the detailed roles of RFRPs in the control of LH secretion. Recent studies have suggested that RFRP-3 neurons in the hypothalamus can regulate the secretion of LH at different levels, including kisspeptin neurons, GnRH neurons, and the pituitary. Additionally, conflicting results regarding the effects of RFRP-3 on these levels exist. In this review, we collect the latest evidence related to the effects of RFRP-3 neurons in regulating LH secretion by acting on kisspeptin neurons, GnRH neurons, and the pituitary and discuss the potential role of the timely reduction of RFRP-3 signaling in the modulation of the preovulatory LH surge.

Regulation of Luteinizing Hormone Receptor mRNA Expression in the Ovary: The Role of miR-122.

The expression of luteinizing hormone receptor (LHR) in the mammalian ovary is regulated in response to changes in the secretion of follicle-stimulating hormone and luteinizing hormone by the anterior pituitary, at least in part, through posttranscriptional mechanisms. The steady-state levels of LHR mRNA are maintained by controlling its rate of degradation by an RNA-binding protein designated as LHR mRNA-binding protein (LRBP). LRBP forms a complex with LHR mRNA and targets it for degradation in the p bodies. miR-122, an 18 nucleotide noncoding RNA, regulates the expression of LRBP. Thus, the levels of miR-122 determine the cellular levels of LHR mRNA expression. This phenomenon has been examined during the induction of LHR mRNA expression that occurs during follicle maturation in response to rising levels of FSH. In this situation, miR-122 and LRBP levels decrease as LHR mRNA expression undergoes downregulation in response to preovulatory LH surge. miR-122 expression as well as LRBP levels show robust increases. The mechanism of induction of LRBP by miR-122 has also been discussed.