LH Secretion Research Articles

Stress rapidly suppresses in vivo LH pulses and increases activation of RFRP-3 neurons in male mice

Restraint stress is a psychosocial stressor that suppresses reproductive status, including LH pulsatile secretion, but the neuroendocrine mechanisms underlying this inhibition remains unclear. Reproductive neural populations upstream of gonadotropin-releasing hormone (GnRH) neurons, such as kisspeptin, neurokinin B and RFRP-3 (GnIH) neurons, are possible targets for psychosocial stress to inhibit LH pulses, but this has not been well examined, especially in mice in which prior technical limitations prevented assessment of in vivo LH pulse secretion dynamics. Here, we examined whether one-time acute restraint stress alters in vivo LH pulsatility and reproductive neural populations in male mice, and what the time-course is for such alterations. We found that endogenous LH pulses in castrated male mice are robustly and rapidly suppressed by one-time, acute restraint stress, with suppression observed as quickly as 12–18 min. This rapid LH suppression parallels with increased in vivo corticosterone levels within 15 min of restraint stress. Although Kiss1, Tac2 and Rfrp gene expression in the hypothalamus did not significantly change after 90 or 180 min restraint stress, arcuate Kiss1 neural activation was significantly decreased after 180 min. Interestingly, hypothalamic Rfrp neuronal activation was strongly increased at early times after restraint stress initiation, but was attenuated to levels lower than controls by 180 min of restraint stress. Thus, the male neuroendocrine reproductive axis is quite sensitive to short-term stress exposure, with significantly decreased pulsatile LH secretion and increased hypothalamic Rfrp neuronal activation occurring rapidly, within minutes, and decreased Kiss1 neuronal activation also occurring after longer stress durations.

Integration of Circadian and Metabolic Control of Reproductive Function.

Optimal fertility in humans and animals relies on the availability of sufficient metabolic fuels, information about which is communicated to the brain via levels of the hormones leptin and insulin. The circadian clock system is also critical; this input is especially evident in the precise timing of the female-specific surge of GnRH and LH secretion that triggers ovulation the next day. Chronodisruption and metabolic imbalance can both impair reproductive activity, and these two disruptions exacerbate each other, such that they often occur simultaneously. Kisspeptin neurons located in the anteroventral periventricular nucleus of the hypothalamus are able to integrate both circadian and metabolic afferent inputs and use this information to modulate the timing and magnitude of the preovulatory GnRH/LH surge. In an environment in which exposure to high caloric diets and chronodisruptors such as artificial night lighting, shift work, and transmeridian travel have become the norm, the implications of these factors for couples struggling to conceive deserve closer attention and more public education.

A study on ghrelin and LH secretion after short fasting and on ghrelin levels at perioestrual period in dairy cattle.

In two experiments, we studied (a) the changes of LH secretion in heifers under different feeding schedules and (b) total ghrelin concentration at oestrus in cows and heifers. In experiment one, synchronized heifers were allocated in three groups (R, regularly fed controls; F, fasted; and F-F fasted-fed). One day after the completion of the oestrous induction protocol, group F and F-F animals stayed without feed for 24hr; thereafter, feed was provided to R and F-F cattle; 2hr later, GnRH was administered to all animals. Blood samples were collected for ghrelin, progesterone, LH and cortisol concentrations. Fasting caused increased ghrelin concentrations in groups F and F-F, while in response to GnRH, LH surge was significantly attenuated in groups F and F-F compared to R. In experiment 2, lactating cows and heifers were used. On day 9 of a synchronized cycle, PGF2α was administered, and blood samples were collected twice daily until the third day after oestrus and analysed for progesterone, estradiol, ghrelin, glucose and BHBA concentrations. No difference was recorded between groups in steroids and BHBA concentrations. In comparison to mid-luteal values, ghrelin concentrations significantly increased at perioestrual period in cows, but not in heifers. This study provides evidence that starving-induced elevated ghrelin concentrations can have suppressing effect on LH secretion, even after ghrelin's restoration to basal values and that during oestrus, ghrelin secretion is differently regulated in cows and heifers, likely being independent from oestradiol concentrations. Further research is required to identify the determining factors that drive the different regulation of ghrelin secretion in cows and heifers.

The Gonadotropin-Releasing Hormone Pulse Generator.

The pulsatile release of GnRH and LH secretion is essential for fertility in all mammals. Pulses of LH occur approximately every hour in follicular-phase females and every 2 to 3 hours in luteal-phase females and males. Many studies over the last 50 years have sought to identify the nature and mechanism of the "GnRH pulse generator" responsible for pulsatile LH release. This review examines the characteristics of pulsatile hormone release and summarizes investigations that have led to our present understanding of the GnRH pulse generator. There is presently little compelling evidence for an intrinsic mechanism of pulse generation involving interactions between GnRH neuron cell bodies. Rather, data support the presence of an extrinsic pulse generator located within the arcuate nucleus, and attention has focused on the kisspeptin neurons and their projections to GnRH neuron dendrons concentrated around the median eminence. Sufficient evidence has been gathered in rodents to conclude that a subpopulation of arcuate kisspeptin neurons is, indeed, the GnRH pulse generator. Findings in other species are generally compatible with this view and suggest that arcuate/infundibular kisspeptin neurons represent the mammalian GnRH pulse generator. With hindsight, it is likely that past arcuate nucleus multiunit activity recordings have been from kisspeptin neurons. Despite advances in identifying the cells forming the pulse generator, almost nothing is known about their mechanisms of synchronicity and the afferent hormonal and transmitter modulation required to establish the normal patterns of LH pulsatility in mammals.

Stimulation with recombinant FSH acutely and significantly increases inhibin B and estradiol in women after GnRH antagonist treatment: a model to study FSH regulation of ovarian function

Obesity is associated with decreased pituitary output of LH and FSH, inadequate folliculogenesis, and reduced ovarian steroid and peptide hormone production. It remains unclear whether the underlying pathophysiology is related to abnormal hypothalamic-pituitary dynamics, abnormal ovarian environment, or both. The persistent deficit in FSH secretion, despite the lack of restraint and normal pituitary FSH reserve, remains unexplained. FSH pulsatility is challenging to evaluate, given its long half-life and low signal-to-noise ratio, and current analytic methods fail to adequately characterize the hormone secretion dynamics of FSH and its feedback. We hypothesized that both Inhibin B and Estradiol (E2) levels will be acutely increased following exogenous, pulsatile recombinant (r) FSH administration, after a GnRH antagonist blockade. This will establish a model to study ovarian, FSH-stimulated E2 and inhibin secretion, independent of the pituitary, to determine mechanisms underlying the FSH/ovarian dysregulation in obesity. A pilot, cohort study of 9 normal-weight, cycling women at the University of Colorado School of Medicine. Participants (mean age 26.3 ± 4.9 years; BMI 22.2 ± 1.3 kg/m2) underwent frequent blood sampling (q10 min) during a 26-hour overnight study visit. Following an initial baseline10-hour collection to assess unstimulated LH and FSH secretion, Cetrotide (EMD Serono) was administered subcutaneously twice: 3 mg at hour 10 and 0.25mg at hour 16. Frequent blood sampling resumed (hours 16-26) and rFSH (Gonal-F; 30 IU) was given intravenously every hour. LH, FSH and E2 were measured by immunoassays (Centaur XP, Siemens). Functional sensitivity is 0.1 mIU/mL and the intra- and inter-assay coefficients of variation were 3.8 and 4.1%, respectively. Inhibin B was analyzed by ELISA (Beckman Coulter). Functional sensitivity is 10 pg/mL and the intra- and inter-assay coefficients of variation were 1.8 and 4.9%, respectively. Statistical significance was determined by paired t test. Normal LH & FSH pulsatility was confirmed for the 10-hour baseline frequent sampling period for all subjects. Administration of Cetrotide reliably suppressed endogenous LH and FSH secretion. Repeated boluses of rFSH mimicked endogenous FSH pulses and significantly increased FSH levels over the course of the infusion (p<0.001). Starting from 6 hours post rFSH administration (after 180 IU) we observed a significant increase in both inhibin B (60%) and E2 (80%) production (p=0.01 and p<0.01 respectively). We herein report that exogenous FSH, administered in a pulsatile fashion after GnRH blockade, induced significant, acute increases in both E2 and Inhibin B, in normal weight women. This experimental paradigm can be used to investigate FSH feedback mechanisms in obesity or other environmental insults impacting ovarian function.

Unripe Papaya Seed Ethanol Extract (Carica papaya, Linn.) Inhibits FSH and LH of Male Mice (Mus musculus)

Family planning is a program designed to control the rate of population growth extensively in the country of Indonesia. In order to avoid of potential destructive effects of population explosion, a nation-wide Family Planning Program has been adopted long-standing in Indonesia. As to make it successful, family planning would have to involve with participation of both males and females. It was aimed to prove that the ethanol extracts of a local plant, Bali papaya, have antifertility function via inhibiting the secretion of FSH and LH. Randomized post-test only control group design was selected for this study. 38 male mice (strain Balb-C) were used and randomly divided into two equal groups. Only 0.5 ml double-distilled water was applicated orally for 36 days to controls; and 0.5 ml ethanol extract of unripe papaya seed with dose of 20 mg/20gr BW/day for 36 days to treatments. At the end of the experimental duration, blood samples of each individuals of both of the groups were collected for FSH and LH measurement. FSH and LH levels in controls were recorded as 3.379 and 15.718 mIU/ml, respectively. In experimental animals, the level of FSH was declined to 2.053 mIU/ml, while LH was measured as 8.626 mIU/ml. The reduction of both of the hormone was probably related to the active substances of extract. Administration of the ethanol extract of papaya seed reduces the average level of FSH and LH (p&lt;0.05), significantly.

Sex-specific changes in postnatal GH and PRL secretion in somatotrope LEPR-null mice.

The developing pituitary is a rapidly changing environment that is constantly meeting the physiological demands of the growing organism. During early postnatal development, the anterior pituitary is refining patterns of anterior hormone secretion in response to numerous genetic factors. Our laboratory previously developed a somatotrope leptin receptor (LEPR) deletion mouse model that had decreased lean body mass, disrupted metabolism, decreased GH stores and was GH deficient as an adult. To understand how deletion of LEPR in somatotropes altered GH, we turned our attention to postnatal development. The current study examines GH, PRL, TSH, ACTH, LH and FSH secretion during postnatal days 4, 5, 8, 10 and 15 and compares age and sex differences. The LEPR mutants have dysregulation of GH (P < 0.03) and a reduced developmental prolactin peak in males (P < 0.04) and females (P < 0.002). There were no differences in weight between groups, and the postnatal leptin surge appeared to be normal. Percentages of immunolabeled GH cells were reduced in mutants compared with controls in all age groups by 35-61% in males and 41-44% in females. In addition, we measured pituitary expression of pituitary transcription factors, POU1F1 and PROP1. POU1F1 was reduced in mutant females at PND 10 (P < 0.009) and PND 15 (P < 0.02) but increased in males at PND 10 (P < 0.01). PROP1 was unchanged in female mutants but showed developmental increases at PND 5 (P < 0.02) and PND 15 (P < 0.01). These studies show that the dysfunction caused by LEPR deletion in somatotropes begins as early as neonatal development and involves developing GH and prolactin cells (somatolactotropes).

Pituitary Action of E2 in Prepubertal Grass Carp: Receptor Specificity and Signal Transduction for Luteinizing Hormone and Follicle-Stimulating Hormone Regulation.

17β-estradiol (E2) is an important sex steroid produced by ovary and brain. In mammals, E2 plays an important role in hypothalamus–pituitary–gonad axis to regulate puberty onset, however, little is known about the functional role of E2 in teleost pituitary. Using prepubertal grass carp as model, three nuclear estrogen receptors (nERs: estrogen receptor alpha, estrogen receptor beta 1, and estrogen receptor beta 2) and two G protein-coupled estrogen receptors (GPER1: GPER1a and GPER1b) were isolated from grass carp pituitary. Tissue distribution analysis indicated that both nERs and GPERs were highly detected in grass carp pituitary, which suggested that E2 should play an important role in grass carp pituitary. Using primary cultured grass carp pituitary cells as model, high-throughput RNA-seq was used to examine the E2-induced differentially expressed genes (DEGs). Transcriptomic analysis showed that E2 could significantly upregulate the expression of 28 genes in grass carp pituitary cells, which were characterized into different functions including reproduction, gonad development, and central nervous system development. Further studies confirmed that E2 could induce luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion and mRNA expression in prepubertal grass carp pituitary in vivo and in vitro. In the pituitary, LH and FSH regulation by E2 were mediated by both ERβ and GPER1. Apparently, E2-induced LHβ and FSHβ mRNA expression were mediated by adenylyl cyclase/cAMP/protein kinase A, phospholipase C/inositol 1,4,5-triphosphate/protein kinase C, and Ca2+/calmodulin/CaM-dependent protein kinase II pathways. In addition to LH and FSH, E2 could also induce growth regulation by estrogen in breast cancer 1 (a novel regulator for pituitary development) mRNA expression in grass carp pituitary cells. These results, as a whole, suggested that E2 could play an important role in gonadotropin hormone release and pituitary development in prepubertal grass carp.

Conspecific odor exposure predominantly activates non-kisspeptin cells in the medial nucleus of the amygdala

A small neuronal subpopulation in the medial nucleus of the amygdala (MeA), expressing the Kiss1 gene, is now considered an important mediator that integrates socio-sexual behavior and odor information in order to modulate the Hypothalamic-Pituitary-Gonadal (HPG) axis. Previous studies demonstrated that exogenous kisspeptin administration or selective activation of Kiss1-expressing neurons in the MeA modulates the onset of puberty, LH secretion and sexual behavior. These functions are supported by the known MeA neuronal connections. In the MeA, as well as in the hypothalamus, Kiss1 mRNA expression mostly depends on sex steroids levels. However, the percentage of Kiss1-expressing cells that co-express estrogen receptor α (ERα) in the MeA is currently unknown. Additionally, whether MeA kisspeptin neurons show Fos expression due to pheromone exposure is still undisclosed. In the present study, we used adult male and female mice that express a reporter protein under the Kiss1 promoters to determine the percentage of Kiss1-expressing neurons that co-express the ERα in the MeA and, whether those cells are activated by olfactory cues. We found a high percentage of Kiss1-expressing neurons in the MeA co-expressing the ERα. The proportion of co-expression was similar between male and female mice in diestrus. Interestingly, a low percentage of Kiss1-expressing neurons in the MeA co-express Fos after conspecific odor exposure, despite a significant increase of Fos positive cells in the MeA. Additionally, odor exposition leads to a sexually dimorphic change in Kiss1 expression in the posterior subdivision of the MeA. Our findings suggest that olfactory signals predominantly activate non-kisspeptin cells in the MeA to modulate responses to pheromones and therefore the HPG axis.

Anti-Müllerian hormone profiling in prepubertal horses and its relationship with gonadal function

Anti-Müllerian hormone (AMH) has gained increasing interest as a biomarker for assessment of gonadal activity. The ability to predict the ovarian follicular reserve of prepubertal female horses (fillies) or to identify stallions with testicular pathologies already during their prepubertal life has not been analyzed so far. Both would help to select fertile horses and reduce costs associated with keeping animals. The objectives of the present study were to (1) assess AMH, LH, FSH, progesterone (females) and testosterone (males) dynamics in prepubertal horses from birth onwards and (2) determine whether AMH concentrations detected in plasma of prepubertal female and male horses are correlated with postpubertal gonadal development. Warmblood foals (n = 30, 14 females, 10 normal males and 6 males with abnormal testicular development) born between February and May of two consecutive years (n = 28 in the first year and n = 2 the next year), were included in the study. Information on gestational length, parity of the dam and placental weight was collected for all foals. Blood samples for hormone analysis were collected from birth onwards every four weeks up to the age of one year. At two years, blood samples were collected on the day when antral follicle count (AFC) and total testicular volume (TTV) were assessed. AMH was detectable in the plasma of all animals from birth onwards and its concentration was significantly higher (P < .001) in males than in females, regardless of testicular development. In males, AMH and testosterone concentration were similar for all animals during the first year of life, regardless of testicular development. At two years, AMH concentration was higher (P < .05) in males with abnormal testicular development than in those with normal testes. In females, AMH concentration at two years was correlated with AMH concentration at birth (P < .05) and with AFC (P < .001). At birth, LH concentration was lower (P < .05) in stallions with abnormal testes (0.3 ± 0.2 ng/ml) than in controls (0.6 ± 0.2 ng/ml). A high negative correlation between AMH concentration and gestation length was observed in males during the first eight weeks of life (P < .01, r = −0.64 to −0.71). Elevated progesterone concentrations over 1 ng/ml were observed in several females starting with 20 weeks of age. This was paralleled by an increase in AMH concentration and was preceded by FSH and LH increases. In conclusion, AMH determination can be reliably used from two years onwards to identify stallions with abnormal testicular development, but it is inconclusive before puberty. In female horses, determination of AMH concentration at a prepubertal age allows for prediction of AMH and AFC after puberty. We suggest that premature luteinisation occurs before the onset of puberty in female horses and that LH secretion in the perinatal period is involved in testicular development and descent in the horse.

Influence of brain plasmalogen changes on gonadotropin secretion from the cultured bovine anterior pituitary cells

We recently discovered that the orphan G-protein–coupled receptor (GPR) 61 colocalized with GnRH receptors (GnRHRs) on the surface of most of bovine gonadotrophs. A recent study suggested that ethanolamine plasmalogen (PI) is a ligand for GPR61 in mouse neuroblastoma. Therefore, this study evaluated the hypothesis that PI alters LH and FSH secretion from cultured bovine anterior pituitary (AP) cells. We prepared bovine AP cells from postpubertal heifers (26 mo old) and cultured the cells for 3.5 d. We treated the cells with increasing concentrations (0, 5, 50, 500, 5,000, 50,000, or 500,000 pg/mL) of phosphoethanolamine PI (PEPI) extracted from the bovine brain, or l-α-lysophosphatidylethanolamine PI (LEPI) extracted from the bovine brain, for 5 min before either no treatment or GnRH stimulation. The medium samples were harvested 2 h after culture for LH and FSH assays. Phosphoethanolamine PI (50–500 pg/mL) stimulated (P < 0.05) the basal secretion of FSH but not LH. Phosphoethanolamine PI at 50 pg/mL also enhanced (P < 0.05) GnRH-induced FSH secretion. However, higher doses (500–500,000 pg/mL) of PEPI suppressed GnRH-induced FSH secretion. Moreover, 50 to 500,000 pg/mL PEPI suppressed GnRH-induced LH secretion. None of the tested concentrations of LEPI showed any effect on basal or GnRH-induced LH or FSH secretion. Pretreatment with Sma and Mad pathway inhibitors suppressed FSH secretion induced by PEPI, whereas an extracellular signal-regulated kinase pathway inhibitor blocked the PEPI-induced suppression of GnRH-stimulated LH secretion. Therefore, PEPI, but not LEPI, extracted from the bovine brain, alters FSH and LH secretion from cultured AP cells. Further studies are required to decide whether PEPI binds to GPR61 and whether PEPI plays an important role in the control of gonadotropin secretion from gonadotrophs.

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.

Bu-shen-zhu-yun decoction promotes synthesis and secretion of FSHβ and LHβ in anterior pituitary cells in vitro

Luteal phase defects (LPD) are an important etiology of infertility which has increased in recent years. Studies have shown that bu-shen-zhu-yun decoction (BSZY-D) can lower the expression of estrogen receptor and progesterone receptor, in rats endometrium of embryonic implantation period, which upregulated by mifepristone, and improve uterine receptivity. The aim of present study was to determine the effect of BSZY-D on the synthesis and secretion of gonadotropic hormones in the anterior pituitary cells of rats. Rats were treated with saline (control) or BSZY-D two times/day for three estrous cycles by gavage. The cerebrospinal fluid (CSF) were collected for further cell treatment. The components in BSZY-D, serum and CSF were analysed by High Performance Liquid Chromatography (HPLC). Cells were either pretreated with normal CSF or BSZY-D/CSF before being stimulated with or without cetrorelix. The mRNA and proteins levels of receptors, hormones, and transcription factors were detected by RT-PCR, western blot analysis and immunostaining. We show that non-toxic concentrations of cetrorelix, a GnRH antagonist, can reduce the mRNA and protein levels of GnRHR, LH, and FSH. This effect could be reversed by the addition of BSZY-D/CSF. We also show decreased mRNA and protein expression of transcription factors, such as CREB, and Egr-1 and secretory vescicles, including SNAP-25 and Munc-18 upon treatment with cetrorelix could be reversed post co-treatment with BSZY-D/CSF. These results indicate that BSZY-D/CSF treatment led to increased levels of GnRHR, transcription factors, and secretory vesicles leading to increased secretion of FSH and LH. Thus, BSZY-D presents a promising candidate to treat luteal phase defects and infertility.

Gonadotrophic pituitary incidentaloma as the cause premature ovarian insufficiency

Objective: evaluate clinical significance pituitary incidentalomas, apparently derived from gonadotropocytes.&#x0D; Design: follow-up study. Patients. Three observations of pituitary microadenomas in patients whose cause for treatment was prolonged amenorrhea. Diagnosed uterine hypoplasia, decreased ovarian reserve, decreased bone mass. Patients combined expressed psycho-emotional symptoms (depression, neuroticism up to mental disorders in one case). The diagnosis of a gonadotrophic incidentaloma is suspected after exclusion of clinical and laboratory signs of prolactinoma, somatotrophic, corticotrophic and thyrotrophic adenoma.&#x0D; Results. In two cases, the clinical picture of severe estrogenic failure was combined with high concentrations FSH, LH and low concentrations of anti-mullerian hormone (AMH). The increase in gonadotrophines, obviously, was both a reaction to a decreased production of estrogens, and the result of their hypersecretion by adenoma. In the observed cases there was no development of ovarian cysts, characteristic for patients with gonadotrophic adenomas, which can be explained by a reduced ovarian reserve. In the third case marked initially normal secretion of FSH and LH, not corresponding to a low concentration of sex steroids. Further there was a complete cessation of the secretion of FSH and LH with a simultaneous rapid decrease in the secretion of AMH. Given the small size of adenomas, in all cases selection of tactics for dynamic observation. All patients were prescribed hormone replacement therapy.&#x0D; Conclusion. For patients with premature ovarian failure, it is advisable to carry out MRI with contrast enhancement to exclude pituitary adenoma.

Neurokinin B receptor agonist and Dynorphin receptor antagonist stimulated luteinizing hormone secretion in fasted male rodents.

Kisspeptin/neurokinin B (NKB)/dynorphin (Dyn) (KNDy) neuron in hypothalamic arcuate nucleus plays a key role in GnRH/LH pulsatile secretion. We aimed to determine whether stimulation of NKB/neurokinin 3 receptor (NK3R) signaling and inhibition of Dyn/kappa-opioid receptor (KOR) signaling recover LH secretion that is suppressed by acute fasting in male rats. Furthermore, we determined dose dependent effect of NKB/NK3R signaling on serum LH level under acute fasting condition in male mice. Mature male rats were injected saline (0.1 mL) and senktide (20 μg/kg), a NK3R agonist, or nor-BNI (800 μg/kg), a KOR antagonist intraperitoneally (ip) after 72 h fasting. And mature male mice were injected multiple doses of senktide, ip after 48 h fasting. Blood and brain sample were collected 90 min after injections for LH measurement and hypothalamic mRNA expressions. All three studies showed significantly lower LH concentration in fasted groups than non-fasted groups. Senktide did not recover LH suppressed by acute fasting in male rats, whereas nor-BNI injected male rats showed significantly higher LH than 72 h fasted male rats (p < 0.05). Mice study showed significantly higher LH concentration in higher doses senktide groups than 48 h fasted group and one of lower doses senktide group. These results suggest that stimulation of NKB/NK3R signaling and attenuation of Dyn/KOR signaling could recover suppressed LH secretion under acute fasting condition in male rodents.

The influence of azaperone treatment at weaning on reproductive function in sows: ovarian activity and endocrine profiles during the weaning-to-ovulation interval

Azaperone can reduce stress caused by weaning and relocation of breeding sows, but its effects on reproductive processes are still poorly understood. The primary aim of this study was to describe and compare the endocrine and ovarian activity in ultrasonographically monitored second parity sows, with or without azaperone treatment at weaning (2 mg/kg BW i.m.). The intervals from weaning to the onset of estrus and ovulation were both greater (P<0.05) in azaperone-treated (n=12) than in control sows (n=12) by ~12 h. Mean daily growth rates of identified antral follicles were less (P<0.05) in azaperone-treated than in control sows (1.08±0.17 v.1.23±0.18 mm/day; mean±SD) and treated animals exceeded (P<0.05) controls in the mean ovulation rate (13.7±1.3 v. 12.6±1.2). A transient suppression of cortisol release was observed in the treatment group (at 10 and 30 min after azaperone injections) but circulating cortisol concentrations were variable in both groups of sows for the remainder of the study. The preovulatory rise in LH and estradiol secretion was delayed (P<0.05), and the duration of the LH surge was greater (P<0.001) in azaperone-treated sows compared with their control counterparts. The amplitude of episodic fluctuations in serum cortisol concentrations was correlated with the number of stillborn piglets in control sows (r=0.63, P=0.04). The amplitude and concentration of the preovulatory rise in estradiol secretion were negatively correlated with ovulatory response and litter size (r=−0.63 to −0.82, P<0.05), whereas the time at which the LH surge ended was directly related to the number of live-born piglets (r=0.82, P=0.002) in azaperone-treated animals. The present results indicate that administration of azaperone at weaning had a profound effect on preovulatory LH secretion as well as growth kinetics and estrogenicity of ovarian antral follicles. However, the causative associations among various characteristics of the preovulatory LH discharge, ovarian and adrenal steroid secretion post-weaning, and reproductive variables in sows remain equivocal.

Anti-Müllerian hormone receptor type 2 is expressed in gonadotrophs of postpubertal heifers to control gonadotrophin secretion.

Preantral and small antral follicles may secret anti-Müllerian hormone (AMH) to control gonadotrophin secretion from ruminant gonadotrophs. The present study investigated whether the main receptor for AMH, AMH receptor type 2 (AMHR2), is expressed in gonadotrophs of postpubertal heifers to control gonadotrophin secretion. Expression of AMHR2 mRNA was detected in anterior pituitaries (APs) of postpubertal heifers using reverse transcription-polymerase chain reaction. An anti-AMHR2 chicken antibody was developed against the extracellular region near the N-terminus of bovine AMHR2. Western blotting using this antibody detected the expression of AMHR2 protein in APs. Immunofluorescence microscopy using the same antibody visualised colocalisation of AMHR2 with gonadotrophin-releasing hormone (GnRH) receptor on the plasma membrane of gonadotrophs. AP cells were cultured for 3.5 days and then treated with increasing concentrations (0, 1, 10, 100, or 1000pgmL-1) of AMH. AMH (10-1000pgmL-1) stimulated (P<0.05) basal FSH secretion. In addition, AMH (100-1000pgmL-1) weakly stimulated (P<0.05) basal LH secretion. AMH (100-1000pgmL-1) inhibited GnRH-induced FSH secretion, but not GnRH-induced LH secretion, in AP cells. In conclusion, AMHR2 is expressed in gonadotrophs of postpubertal heifers to control gonadotrophin secretion.

Biostimulation in primiparous postpartum acyclic early weaned beef cows: introducing the bulls at weaning advances cyclic rebreeding.

Weaning and biostimulation promote an early cyclic postpartum rebreeding. Although the signals and mechanisms by which weaning and biostimulation differ, both end stimulating LH secretion. The aim of the experiment was to determine if weaning and biostimulation have additive effects advancing the postpartum rebreeding in primiparous postpartum anoestrous cows. The experiment was performed during late spring – early summer with 51 primiparous Hereford cows. Six weeks after parturition calves were weaned, and cows were managed in two experimental groups: WB (n = 22) and WDB (n = 29). Bulls were joined with WB cows at weaning, but joining was delayed one week in WDB cows. The presence of corpora lutea in the ovaries was recorded weekly with ultrasound, and 28 and 50 days after the end of the exposure period, pregnancy was determined by ultrasound. The percentage of cyclic cows was greater in WB than in WDB on Weeks 8 (36.4 vs 0%), 9 68.2 vs 13.8%), 10 (86.4 vs 27.6%) and 11 (100.0 vs 37.9%) (P < 0.001 in all). Cows that were weaned and biostimulated simultaneously rebred earlier than WDB cows (Week 9.1 ± 0.2 vs Week 11.0 ± 0.2; P < 0.0001). At the end of the experiment 46/51 (90.2%) of the animals were cycling. Pregnancy rate tended to be greater in WB than WDB cows 28 days after the end of the breeding period 18/22 vs 17/29, P = 0.077), but there was no difference at the end of the study (20/22 vs 24/29, ns). In conclusion, the application of weaning and biostimulation simultaneously advances postpartum rebreeding more than weaning alone in beef cows.

Kisspeptin and polycystic ovary syndrome - is there any connection?

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders in women of reproductive age. It is known that kisspeptin stimulates activity of GnRH neurons and secretion of FSH and LH, thus disruption of interaction between kisspeptin and its receptor leads to anovulation. The aim of the study was to investigate the role kisspeptin in the pathogenesis of polycystic ovary syndrome. Materials and methods. The study included 14 patients with classic phenotype of PCOS and 11 healthy women of the control group. All the patients underwent laparoscopy and hysteroscopy with histological examination of ovarian tissue and endometrium. Determination of kisspeptin, FSH, LH, prolactin, AMH, estradiol, estrone, androgens (free testosterone and dehydroepiandrosterone sulfate) levels in peripheral blood in healthy women and patients with PCOS was performed by ELISA on the 2d and 8th days of menstrual cycle. Progesterone levels were investigated on the 18th-22d days of menstrual cycle. Expression of kisspeptin and its receptor in ovarian tissue and endometrium was estimated using immunohistochemical method. Results. Level of kisspeptin in peripheral blood of patients with PCOS tends to increase compared to its level in the control group, but the found difference was not reliable. Direct correlation between serum level of kisspeptin and levels of LH, free testosterone and DHEA-S was revealed in patients with PCOS. Immunohistochemical study in patients with PCOS showed a significant increase in the area of expression of КІЅЅ1 and KISS1R receptor in endometrium and in ovarian biopsies compared to these values in the control group. Conclusion. The obtained data show a definite role of kisspeptin in pathogenesis of polycystic ovary syndrome, but further research is needed.

Expression of hypothalamic kisspeptin, neurokinin B, and dynorphin A neurons attenuates in female Zucker fatty rats.

Zucker fatty (ZF) rats are considered to be an obese model due to leptin receptor abnormality and such rats show infertility. Pulsatile gonadotropin-releasing hormone/luteinizing hormone (LH) secretion, which is important for follicular development in females, is considered to be controlled by KNDy neurons coexpressing kisspeptin, neurokinin B (NKB), and dynorphin A (DynA), encoded by Kiss1, Tac3, and Pdyn, respectively, in the hypothalamic arcuate nucleus (ARC). The purpose of this study is to examine the expression of KNDy neurons in female ZF rats by histochemical approach because pulsatile LH secretion is suppressed. Zucker lean (ZL) rats served as a control group. Animals were ovariectomized and subcutaneously implanted with a silicon tube containing estradiol to produce plasma level of estradiol during diestrus. Plasma LH levels decreased in ZF rats compared with ZL rats. The expressions of each mRNA (Kiss1, Tac3, and Pdyn) and each peptide (kisspeptin, NKB, and DynA) in the ARC significantly decreased in ZF rats compared with ZL rats. However, the number of Kiss1 neurons in the anterior ventral periventricular nucleus did not significantly differ between the two groups. These results suggest that dysfunction of leptin signaling negatively affects KNDy neurons in the ARC, resulting in reproductive dysfunction caused by suppression of the LH pulse.