scholarly journals Differential Effects of Gonadotropin-Releasing Hormone (GnRH) Pulse Frequency on Gonadotropin Subunit and GnRH Receptor Messenger Ribonucleic Acid Levels in Vitro*

Endocrinology ◽  
1997 ◽  
Vol 138 (3) ◽  
pp. 1224-1231 ◽  
Author(s):  
Ursula B. Kaiser ◽  
Andrzej Jakubowiak ◽  
Anna Steinberger ◽  
William W. Chin

Abstract The hypothalamic hormone, GnRH, is released and transported to the anterior pituitary in a pulsatile manner, where it binds to specific high-affinity receptors and regulates gonadotropin biosynthesis and secretion. The frequency of GnRH pulses changes under various physiological conditions, and varying GnRH pulse frequencies have been shown to regulate differentially the secretion of LH and FSH and the expression of the gonadotropin α, LHβ, and FSHβ subunit genes in vivo. We demonstrate differential effects of varying GnRH pulse frequency in vitro in superfused primary monolayer cultures of rat pituitary cells. Cells were treated with 10 nm GnRH pulses for 24 h at a frequency of every 0.5, 1, 2, or 4 h. α, LHβ, and FSHβ messenger RNA (mRNA) levels were increased by GnRH at all pulse frequencies. α and LHβ mRNA levels and LH secretion were stimulated to the greatest extent at a GnRH pulse frequency of every 30 min, whereas FSHβ mRNA levels and FSH secretion were stimulated maximally at a lower GnRH pulse frequency, every 2 h. GnRH receptor (GnRHR) mRNA levels also were increased by GnRH at all pulse frequencies and were stimulated maximally at a GnRH pulse frequency of every 30 min. Similar results were obtained when the dose of each pulse of GnRH was adjusted to maintain a constant total cumulative dose of GnRH over 24 h. These data show that gonadotropin subunit gene expression is regulated differentially by varying GnRH pulse frequencies in vitro, suggesting that the differential effects of varying GnRH pulse frequencies on gonadotropin subunit gene expression occur directly at the level of the pituitary. The pattern of regulation of GnRHR mRNA levels correlated with that of α and LHβ but was different from that of FSHβ. This suggests that α and LHβ mRNA levels are maximally stimulated when GnRHR levels are relatively high, whereas FSHβ mRNA levels are maximally stimulated at lower levels of GnRHR expression, and that the mechanism for differential regulation of the gonadotropins by varying pulse frequencies of GnRH may involve levels of GnRHR. Furthermore, these data suggest that the mechanisms whereby varying GnRH pulse frequencies stimulate α, LHβ, and GnRHR gene expression are similar, whereas the stimulation of FSHβ mRNA levels may be different.

Fishes ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 48 ◽  
Author(s):  
Kristine von Krogh ◽  
Erik Ropstad ◽  
Rasoul Nourizadeh-Lillabadi ◽  
Trude Marie Haug ◽  
Finn-Arne Weltzien

Bisphenol A (BPA) and tetrabromobisphenol A (TBBPA) are widely used industrial chemicals, ubiquitously present in the environment. While BPA is a well-known endocrine disruptor and able to affect all levels of the teleost reproductive axis, information regarding TBBPA on this subject is very limited. Using primary cultures from Atlantic cod (Gadus morhua), the present study was aimed at investigating potential direct effects of acute (72 h) BPA and TBBPA exposure on cell viability and the expression of reproductive-relevant genes in the pituitary. The results revealed that both bisphenols stimulate cell viability in terms of metabolic activity and membrane integrity at environmentally relevant concentrations. BPA had no direct effects on gonadotropin gene expression, but enhanced the expression of gonadotropin-releasing hormone (GnRH) receptor 2a, the main gonadotropin modulator in Atlantic cod. In contrast, TBBPA increased gonadotropin transcript levels but had no effect on GnRH receptor mRNA. In conclusion, both anthropogenic compounds display endocrine disruptive properties and are able to directly interfere with gene expression related to reproductive function in cod pituitary cells at environmentally relevant concentrations in vitro.


Endocrinology ◽  
2000 ◽  
Vol 141 (7) ◽  
pp. 2285-2293 ◽  
Author(s):  
Kazunori Kageyama ◽  
Georges E. Gaudriault ◽  
Margaret J. Bradbury ◽  
Wylie W. Vale

CRF receptor type 2 (CRF R2) messenger RNA (mRNA) expression in the rodent heart is modulated by exposure to both the bacterial endotoxin lipopolysaccharide (LPS) and glucocorticoids. In this study we examined the roles of glucocorticoids, cytokines, and CRF R2β ligands in the regulation of CRF R2β expression in the cardiovascular system both in vivo and in vitro. Using ribonuclease protection assays, we found that, in addition to the injection of LPS or corticosterone, physical restraint caused a decrease in CRF R2β mRNA levels in the rat heart and aorta. Adrenalectomy with corticosterone replacement at constant levels partially blocked LPS-induced decreases in CRF R2β mRNA expression in the heart. Thus, elevations of endogenous circulating corticosterone could contribute to the down-regulation of CRF R2β mRNA expression in heart. To identify other putative modulating factors, we examined CRF R2β expression in the aorta- derived A7R5 cell line. Incubation with CRF R2 ligands or dexamethasone reduced CRF R2β mRNA levels. In addition, incubation with a variety of cytokines, proteins released during immune challenge, also reduced CRF R2β mRNA expression. The multifactorial regulation of CRF R2β mRNA expression in the cardiovascular system may serve to limit the inotropic and chronotropic effects of CRF R2 agonists such as urocortin during prolonged physical or immune challenge.


2013 ◽  
Vol 25 (1) ◽  
pp. 187
Author(s):  
M. J. Sudano ◽  
E. S. Caixeta ◽  
D. M. Paschoal ◽  
T. S. Rascado ◽  
L. F. Crocomo ◽  
...  

Over the past decades, there have been great advances in in vitro production (IVP) systems with improved culture methods and new knowledge regarding embryo genetics, physiology, ultrastructure, and morphology. Nevertheless, a major obstacle for dissemination of this technology is the great sensitivity of IVP embryos to cryopreservation. The objective was to study the global gene-expression patterns of fresh and vitrified IVP bovine embryos. Oocytes (N = 1290) were matured and fertilized in vitro (Day 0). Presumptive zygotes were cultured in SOFaa with 0.5% BSA and 2.5% of FCS. Cleavage and blastocyst production was evaluated after 3 and 7 days under standard culture conditions (at 38.5°C in atmosphere of 5% O2, 5% CO2, and 90% N2). On Day 7, half of the blastocysts were vitrified (n = 94), warmed (Sudano et al. 2011 Theriogenology 75, 1211–1220), and returned for 24 h of additional culture (re-expansion and hatching; hatched was evaluated 12 and 24 h after warming, respectively) when their RNA was extracted (vitrified group). The remaining embryos returned to culture until Day 8 when their RNA was extracted (fresh group). Total RNA extraction of a single blastocyst was performed using the PicoPure Kit (Applied Biosystems®, Foster City, CA, USA). The RNA samples were DNAse treated (Qiagen®, Valencia, CA, USA), and mRNA was amplified (RiboAmp Kit®). The aRNA output was evaluated with a NanoDrop (Thermo®, Wilmington, DE, USA) and Bioanalyzer (Agilent®, Santa Clara, CA, USA). Biotin-labelled and fragmented cRNA were obtained with the 3′IVT Kit (Affymetrix®, Santa Clara, CA, USA) to perform hybridization (N = 6–7, respectively, for vitrified and fresh groups) using the GeneChip Bovine Array (Affymetrix®). Microarray data analysis was performed with the FlexArray 1.6.1.1. Genes with a fold change of at least 2 and a probability of P ≤ 0.05 were considered differentially expressed. Real-time PCR was used to validate microarray results (N = 11–15, respectively, for vitrified and fresh groups). As a control, a pool of 200 blastocysts was submitted or not to mRNA amplification followed by the reverse transcription and qPCR of 17 genes. For statistical analyses, PROC GLIMMIX, PROC LOGISTIC, and PROC CORR were used. Cleavage and blastocyst production rates were 86.8 ± 1.0 and 32.5 ± 1.9%, respectively. Re-expansion and hatching/hatched rates were 69.3 and 19.3%, respectively. Messenger RNA abundance of amplified and nonamplified RNA had a high correlation (r = 0.89, P < 0.01). The microarray analysis indicated 383 differentially expressed genes (P ≤ 0.05) between fresh and vitrified blastocysts. Genes involved in apoptosis (PRDX2), heat shock (HSPA5), maternal recognition of pregnancy (IFNT2 and PAG2), and cell differentiation and placenta formation (KRT18) were downregulated in vitrified embryos. According to qPCR analysis, mRNA abundance of IFNT2, PRDX2, and KRT18 was downregulated, whereas HSPA5 mRNA levels were upregulated in vitrified blastocysts. Messenger RNA abundance of PAG2 was not different (P = 0.46) between fresh and vitrified embryos. In conclusion, vitrification alters the expression profile of the genes IFNT2, PRDX2, KRT18, and HSPA5 that can be related with embryo postcryopreservation survival capacity. FAPESP and LNBio-CNPEM are acknowledged.


2002 ◽  
Vol 175 (3) ◽  
pp. 605-613 ◽  
Author(s):  
K Rousseau ◽  
N Le Belle ◽  
M Sbaihi ◽  
J Marchelidon ◽  
M Schmitz ◽  
...  

The regulation of growth hormone (GH) by thyroid hormones (THs) has been shown to present species variation. We investigated the regulation of GH in the eel, a representative of an ancient group of teleosts. In vivo administration of triiodothyronine (T(3)) or thyroxine (T(4)) significantly reduced pituitary and serum GH levels, as measured by homologous RIA. In order to investigate the ability of THs to regulate GH production directly at the pituitary level, we used a long-term, serum-free primary culture of eel pituitary cells. Both T(3) and T(4) inhibited GH release in a concentration-dependent manner, producing up to 50% inhibition at 10 nM, with an ED(50) of <0.2 nM, within the range of their physiological circulating levels. Other hormones also acting via the nuclear receptor superfamily, such as sex steroids (testosterone, estradiol and progesterone) and corticosteroid (cortisol), had no effect on GH release in vitro, underlining the specificity of the regulatory effect of THs on GH. Measurement of both GH release and cellular content for calculation of GH production in vitro indicated that THs not only inhibited GH release but also GH synthesis. Dot-blot assay of GH messenger RNA (mRNA) using an homologous eel cDNA probe showed a decrease in GH mRNA levels in cells cultured in the presence of T(3), as compared with control cells. This demonstrated that the inhibition of T(3) on GH synthesis was mediated by a decrease in GH mRNA steady state levels. In conclusion, we demonstrate inhibitory regulation of eel GH synthesis and release by THs, exerted directly at the pituitary level. These data contrast with the rat, where THs are known to have a stimulatory effect and suggest that the pattern observed here in an early vertebrate and also found in birds, reptiles and some mammals including humans, may represent an ancestral and more generalized vertebrate pattern of TH regulation of pituitary GH.


Endocrinology ◽  
1998 ◽  
Vol 139 (2) ◽  
pp. 474-478 ◽  
Author(s):  
Charles C. Gregory ◽  
Carlton E. Dean ◽  
Tom E. Porter

Abstract The importance of thyroid hormone from embryonic through neonatal life has been documented in both avian and mammalian species. However, the regulation of thyroid hormone production during this period is not completely understood. The objective of this study was to characterize expression of chicken TSHβ messenger RNA (mRNA) compared with that of thyroid hormones and GH in embryonic and neonatal chickens. Total pituitary RNA was extracted on embryonic days (e-) 11, 13, 15, 17, and 19 and neonatal days (d-) 1, 3, 6, 9, and 12 and subjected to ribonuclease protection assays (RPA) for chicken TSHβ mRNA. TSHβ mRNA levels increased through e-19, with e-19 levels being greater than those at all other embryonic ages (P &lt; 0.05). Levels decreased markedly on d-1, then slowly increased to d-6 and stayed elevated through d-12. RIAs were performed for T4, T3, and GH at the same ages. Serum T4 levels increased slowly from less than 1.0 ng/ml on e-11 to a peak of 6.6 ng/ml on d-1 (P &lt; 0.05). After the peak on d-1, posthatch T4 levels stabilized between 3.5–4.5 ng/ml through d-12 (P &lt; 0.05). T3 concentrations were less than 0.25 ng/ml on e-11, increased dramatically between e-19 and d-1 (P &lt; 0.05), and remained high throughout the rest of the experiment, with a concentration of 3.25 ng/ml on d-6 (P &lt; 0.05). GH levels for e-11 through e-17 were below the sensitivity of the GH RIA. On e-19, the GH level was 3 ng/ml and continued to increase through d-12 to a level of 130 ng/ml. As thyroid hormone levels were preceded by maximal TSHβ mRNA levels on e-19, we next determined whether TSHβ gene expression on e-19 was under TRH and T3 regulation. E-19 anterior pituitary cells were cultured in serum-free medium with either TRH (10−8) or T3 (10−8) for 20–24 h. Treatment with T3 significantly decreased levels of TSHβ mRNA (P &lt; 0.05). However, TRH did not produce a significant increase in TSHβ mRNA, although TRH did increase TSHβ mRNA by 60%, on the average, in this study. Therefore, these results indicate that an increase in pituitary TSH production probably regulates thyroid hormone levels during late embryonic development and that negative feedback inhibition of TSH production by thyroid hormones also exists at this critical developmental stage.


1998 ◽  
Vol 83 (2) ◽  
pp. 448-452
Author(s):  
H. F. Erden ◽  
I. H. Zwain ◽  
H. Asakura ◽  
S. S. C. Yen

Recently, we reported that the thecal compartment of the human ovary contains a CRF system replete with gene expression and protein for corticotropin-releasing factor (CRF), CRF-Receptor 1 (CRF-R1), and the blood-derived high affinity CRF-binding protein (CRF-BP). Granulosa cells are devoid of the CRF system. The parallel increases in intensity of CRF, CRF-R1, and 17α-hydroxylase messenger ribonucleic acid (mRNA) and proteins in thecal cells with follicular maturation suggest that the intraovarian CRF system may play an autocrine role regulating androgen biosynthesis, with a downstream effect on estrogen production by granulosa cells. The functionality of the ovarian CRF system may be conditioned by the relative presence of plasma-derived CRF-BP by virtue of its localization of protein, but not transcript in thecal cells and its ability to compete with CRF for the CRF receptor. To further these findings, in the present study we have examined the effect of CRF on LH-stimulated 17α-hydroxylase (P450c17) gene expression and androgen production by isolated thecal cells from human ovarian follicles (11–13 mm). During the 48-h culture, addition of LH (10 ng/mL) to the medium increased by 5- and 6-fold dehydroepiandrosterone and androstenedione production by thecal cells. Remarkably, the LH-stimulated, but not basal, androgen production was inhibited by CRF in a time- and dose-dependent manner. The half-maximal (ID50) effect dose of CRF occurred at 5 × 10−8 mol/L, and at a maximal concentration of 10−6 mol/L, CRF completely inhibited LH-stimulated androgen production. This inhibitory effect of CRF became evident at 12 h (45%), and by 24 h the effect was more pronounced, with a 70% reduction from baseline. As determined by Northern analyses, CRF dose dependently decreased LH-stimulated P450c17 mRNA levels, with a maximal inhibition of 85% P450c17 gene expression at a CRF concentration of 10−6 mol/L. With the addition of 10−6 mol/L of the antagonist α-helical CRF-(9–41), the inhibitory effect of CRF was partially reversed for both P450c17 mRNA (75%) and androgen production (50%), indicating the CRF-R1-mediated event. In conclusion, the present study demonstrated a potent inhibitory effect of CRF on LH-stimulated dehydroepiandrosterone and androstenedione production that appears to be mediated through the reduction of P450c17 gene expression. Thus, the ovarian CRF system may function as autocrine regulators for androgen biosynthesis in the thecal cell compartment to maintain optimal substrate for estrogen biosynthesis by granulosa cells. Further studies to define the role of CRF-BP in the endocrine modulation of the intraovarian CRF system are needed.


Endocrinology ◽  
1999 ◽  
Vol 140 (10) ◽  
pp. 4644-4650 ◽  
Author(s):  
Eric Dumonteil ◽  
Beate Ritz-Laser ◽  
Chistophe Magnan ◽  
Iléana Grigorescu ◽  
Alain Ktorza ◽  
...  

Abstract α cell function is impaired in diabetes. In diabetics, plasma levels of glucagon are high despite persistently elevated glucose levels and may even rise paradoxically in response to a glucose load; high plasma glucagon levels are accompanied by increased proglucagon gene expression. We have investigated the effects of high glucose concentrations on InR1G9 cells, a glucagon-producing cell line. We show here that chronically elevated glucose concentrations increase glucagon release by 2.5- to 4-fold, glucagon cell content by 2.5- to 3-fold, and proglucagon messenger RNA levels by 4- to 8-fold, whereas changes for 24 h have no effect on proglucagon messenger RNA levels. Persistently elevated glucose affects proglucagon gene expression at the level of transcription and insulin is capable of preventing this effect. We conclude that chronically elevated glucose may be an important factor in the α cell dysfunction that occurs in diabetes and thus that glucose may not only affect the β cell but also the α cell.


2003 ◽  
Vol 31 (1) ◽  
pp. 233-239 ◽  
Author(s):  
M Karamouti ◽  
P Kollia ◽  
E Karligiotou ◽  
A Kallitsaris ◽  
N Prapas ◽  
...  

Whether leptin is secreted by the human ovary is not known. The available data on leptin gene (ob gene) expression by human granulosa cells are conflicting. The aim of the present study was first to re-examine the expression of leptin messenger RNA (mRNA) by human granulosa cells and second to investigate if these cells have the ability to secrete leptin in cultures. Human luteinized granulosa cells were obtained from normal women undergoing in vitro fertilisation treatment after ovarian stimulation and follicle aspiration. The expression of ob gene was studied by Reverse-Transcriptase Polymerase Chain Reaction (RT-PCR) both in primary granulosa cells treated immediately after oocyte recovery and in cells cultured up to 24 h under baseline and hormonally stimulated conditions (FSH: 100 ng/ml, LH: 100 ng/ml). ob mRNA transcripts were not detected in luteinized granulosa cells, while they were present in adipose tIssue cDNA. Actin gene expression was detected in all studied samples. Using a sensitive radioimmunoassay (lower limit of detection 0.05 ng/ml), leptin was undetectable in the culture media at all points during the 72 h cultures, while at the same time significant amounts of oestradiol and progesterone were produced particularly after the addition of androstendione (1 microM) to the incubation media. These results demonstrate for the first time that leptin is not secreted by human luteinized granulosa cells in cultures. From a physiological point of view, this may contribute to the development of the optimal follicular environment for oocyte maturation during the preovulatory period.


Animals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 462 ◽  
Author(s):  
George Ramirez ◽  
Jaime Palomino ◽  
Karla Aspee ◽  
Monica De los Reyes

The competence to undergo expansion is a characteristic of cumulus cells (CCs). The aim was to investigate the expression of GDF-9 and BMP-15 mRNA in canine cumulus cells in relation to cumulus expansion and meiotic development over the estrous cycle. CCs were recovered from nonmatured and in vitro-matured (IVM) dog cumulus oocyte complexes (COCs), which were obtained from antral follicles at different phases of the estrous cycle. Quantitative real-time polymerase chain reaction (q-PCR) was used to evaluate the relative abundance of GDF-9 and BMP-15 transcripts from the CCs with or without signs of expansion. The results were evaluated by ANOVA and logistic regression. The maturity of the oocyte and the expansion process affected the mRNA levels in CCs. There were differences (p < 0.05) in GDF-9 and BMP-15 gene expression in CCs isolated from nonmatured COCs when comparing the reproductive phases. Lower mRNA levels (p < 0.05) were observed in anestrus and proestrus in comparison to those in estrus and diestrus. In contrast, when comparing GDF-9 mRNA levels in IVM COCs, no differences were found among the phases of the estrous cycle in expanded and nonexpanded CCs (p < 0.05). However, the highest (p < 0.05) BMP-15 gene expression in CCs that did not undergo expansion was exhibited in anestrus and the lowest (p < 0.05) expression was observed in estrus in expanded CCs. Although the stage of the estrous cycle did not affect the second metaphase (MII )rates, the expanded CCs obtained at estrus coexisted with higher percentages of MII (p < 0.05). In conclusion, the differential expression patterns of GDF-9 and BMP-15 mRNA transcripts might be related to cumulus expansion and maturation processes, suggesting specific regulation and temporal changes in their expression.


Sign in / Sign up

Export Citation Format

Share Document