Homologous Upregulation of GnRH Receptor mRNA by Continuous GnRH in Cultured Rat Pituitary Cells

Cheon, Minseok; Park, Deokbae; Kim, Kyungjin; Park, Sang Dai; Ryu, Kyungza

doi:10.1385/endo:11:1:49

Cited by 17 publications

(9 citation statements)

References 35 publications

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“…These in vitro results are in line with the finding in cultured rat pituitary cells of increased GnRH-R mRNA levels on exposure to GnRH [38]. However, the peak in rat was achieved faster (6 h) than in tilapia, and the response was already evident at a lower dose of the peptide (2 nM).…”

Section: Discussionsupporting

confidence: 89%

Regulation of Gonadotropin-Releasing Hormone (GnRH)-Receptor Gene Expression in Tilapia: Effect of GnRH and Dopamine1

Levavi‐Sivan¹,

Safarian²,

Rosenfeld

et al. 2004

Biology of Reproduction

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The present work was designed to study certain aspects of the endocrine regulation of gonadotropin-releasing hormone receptor (GnRH-R) in the pituitary of the teleost fish tilapia. A GnRH-R was cloned from the pituitary of hybrid tilapia (taGnRH-R) and was identified as a typical seven-transmembrane receptor. Northern blot analysis revealed a single GnRH-R transcript in the pituitary of approximately 2.3 kilobases. The taGnRH-R mRNA levels were significantly higher in females than in males. Injection of the salmon GnRH analog (sGnRHa; 5-50 microg/kg) increased the steady-state levels of taGnRH-R mRNA, with the highest response recorded at 25 microg/kg and at 36 h. At the higher dose of sGnRHa (50 microg/kg), taGnRH-R transcript appeared to be down-regulated. Exposure of tilapia pituitary cells in culture to graded doses (0.1-100 nM) of seabream (sbGnRH = GnRH I), chicken II (cGnRH II), or salmon GnRH (sGnRH = GnRH III) resulted in a significant increase in taGnRH-R mRNA levels. The highest levels of both LH release and taGnRH-R mRNA levels were recorded after exposure to cGnRH II and the lowest after exposure to sbGnRH. The dopamine-agonist quinpirole suppressed LH release and mRNA levels of taGnRH-R, indicating an inhibitory effect on GnRH-R synthesis. Collectively, these data provide evidence that GnRH in tilapia can up- regulate, whereas dopamine down-regulates, taGnRH-R mRNA levels.

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Section: Discussionsupporting

confidence: 89%

Regulation of Gonadotropin-Releasing Hormone (GnRH)-Receptor Gene Expression in Tilapia: Effect of GnRH and Dopamine1

Levavi‐Sivan¹,

Safarian²,

Rosenfeld

et al. 2004

Biology of Reproduction

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“…Consistent with the hypothesis that the decline in Gnrhr expression in pituitary cells reflects the loss of GnRH, its continuous application caused recovery of Gnrhr expression with a peak in response after 6 to 8 h stimulation. Others also observed stimulatory effect of GnRH on Gnrhr expression in rat pituitary cells during 6 h continuous application [44]. This recovery was transient, followed by decay in expression during continuous GnRH application, which did not go below the steady-state level established during the 2-day incubation, i.e.…”

Section: Discussionmentioning

confidence: 85%

The relationship between basal and regulated Gnrhr expression in rodent pituitary gonadotrophs

Bjelobaba

Janjic

Tavcar

et al. 2016

Molecular and Cellular Endocrinology

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Hypothalamic GnRH together with gonadal steroids and activins/inhibin regulate its receptor gene (Gnrhr) expression in vivo, which leads to crucial changes in GnRHR numbers on the plasma membrane. This is accompanied by alterations in the gonadotroph sensitivity and responsiveness during physiologically relevant situations. Here we investigated basal and GnRH-regulated Gnrhr expression in rodent pituitary gonadotrophs in vitro. In pituitary cells from adult animals cultured in the absence of GnRH and steroid hormones, the Gnrhr expression was progressively reduced but not completely abolished. The basal Gnrhr expression was also operative in LβT2 immortalized gonadotrophs never exposed to GnRH. In both cell types, basal transcription was sufficient for the expression of functional GnRHRs. Continuous application of GnRH transiently elevated the Gnrhr expression in cultured pituitary cells followed by a sustained fall without affecting basal transcription. Both basal and regulated Gnrhr transcriptions were dependent on the protein kinase C signaling pathway. The GnRH-regulated Gnrhr expression was not operative in embryonal pituitary and LβT2 cells and was established neonatally, the sex-specific response patterns were formed at the juvenile-peripubertal stage and there was a strong correlation between basal and regulated gene expression during development. Thus, the age-dependent basal and regulated Gnrhr transcription could account for the initial blockade and subsequent activation of the reproductive system during development.

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“…The lack of effect of GnRH treatment on Lhb expression was also observed in pituitary cells from ovariectomized rats 39 . In contrast to gonadotropin subunit genes, previous experiments have well clarified that expression of Gnrhr decays during prolonged culturing in the absence and presence of GnRH 26,40,41 . GnRH treatment also elevates Dmp1 expression in vitro with similar kinetics and concentration dependence 27,42 .…”

Section: Discussionmentioning

confidence: 99%

Divergent expression patterns of pituitary gonadotropin subunit and GnRH receptor genes to continuous GnRH in vitro and in vivo

Janjic

Prévide

Fletcher

et al. 2019

Sci Rep

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Continuous, as opposed to pulsatile, delivery of hypothalamic gonadotropin-releasing hormone (GnRH) leads to a marked decrease in secretion of pituitary gonadotropins LH and FSH and impairment of reproductive function. Here we studied the expression profile of gonadotropin subunit and GnRH receptor genes in rat pituitary in vitro and in vivo to clarify their expression profiles in the absence and continuous presence of GnRH. Culturing of pituitary cells in GnRH-free conditions downregulated Fshb, Cga, and Gnrhr expression, whereas continuous treatment with GnRH agonists upregulated Cga expression progressively and Gnrhr and Fshb expression transiently, accompanied by a prolonged blockade of Fshb but not Gnrhr expression. In contrast, Lhb expression was relatively insensitive to loss of endogenous GnRH and continuous treatment with GnRH, probably reflecting the status of Egr1 and Nr5a1 expression. Similar patterns of responses were observed in vivo after administration of a GnRH agonist. However, continuous treatment with GnRH stimulated LH secretion in vitro and in vivo, leading to decrease in LH cell content despite high basal Lhb expression. These data suggest that blockade of Fshb expression and depletion of the LH secretory pool are two major factors accounting for weakening of the gonadotroph secretory function during continuous GnRH treatment.

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Homologous Upregulation of GnRH Receptor mRNA by Continuous GnRH in Cultured Rat Pituitary Cells

Cited by 17 publications

References 35 publications

Regulation of Gonadotropin-Releasing Hormone (GnRH)-Receptor Gene Expression in Tilapia: Effect of GnRH and Dopamine1

Regulation of Gonadotropin-Releasing Hormone (GnRH)-Receptor Gene Expression in Tilapia: Effect of GnRH and Dopamine1

The relationship between basal and regulated Gnrhr expression in rodent pituitary gonadotrophs

Divergent expression patterns of pituitary gonadotropin subunit and GnRH receptor genes to continuous GnRH in vitro and in vivo

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