Differential Expression of c-fos In Vitro by All Anterior Pituitary Cell Types During the Estrous Cycle: Enhanced Expression by Luteinizing Hormone but Not by Follicle-stimulating Hormone Cells

Armstrong, Jennifer; Childs, Gwen V.

doi:10.1177/002215549704500603

Cited by 9 publications

(17 citation statements)

References 44 publications

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“…The present studies and recent publications (Cesnjaj et al 1994;Armstrong and Childs 1997b) provide proof that normal gonadotropes express fos. In our recent study, the highest expression of fos by pituitary gonadotropes (metestrus) did not coincide with the highest expression of GnRH receptors (Lloyd and Childs 1988) (proestrus).…”

Section: Effects Of Gnrh On Fos Proteinssupporting

confidence: 85%

“…However, the dual labeling evidence indicated that most of the fos-bearing cells in this population are not gonadotropes (Armstrong and Childs 1997b). This initially raised a question about fos as a third messenger in the activation of the gonadotrope during proestrus and led to subsequent studies designed to learn if GnRH can stimulate fos expression by gonadotropes from proestrous rats.…”

Section: Discussionmentioning

confidence: 99%

“…Cesnjaj et al (1994) also reported that GnRH stimulated c-fos in primary pituitary cell cultures from randomly cycling female rats, as well as c-fos, c-jun, and jun-B in the ␣ T3-1 gonadotrope cell line. Recent studies in our laboratory con-firm that c-fos is expressed by gonadotropes, particularly those bearing luteinizing hormone-␤ (LH ␤ ) antigens or mRNA (Armstrong and Childs 1997b).…”

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confidence: 96%

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Regulation of c-fos Expression by EGF and GnRH in Specific Anterior Pituitary Cells from Proestrous Female Rats

Armstrong

Childs

1998

J Histochem Cytochem.

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SUMMARY C-fos is an early expression oncogene that can be stimulated by a variety of regulators. It is expressed by subsets of all pituitary cells, with increased expression seen in proestrous rats. However, in freshly dispersed pituitary cells studied during different stages of the cycle, there is limited expression of fos by luteinizing hormone (LH) cells and little basal expression by cells with follicle-stimulating hormone (FSH) antigens. Proestrus is a time during which pituitary gonadotropes express peak levels of receptors for gonadotropin-releasing hormone (GnRH) and epidermal growth factor (EGF). We hypothesized that if GnRH or EGF stimulated fos activity in gonadotropes they would be most effective during the peak expression of their receptors. Anterior pituitaries were removed, cut into small pieces, and stimulated for 30 min. Total RNA was then collected and analyzed by Northern analysis. Both EGF and GnRH caused an increase in c-fos mRNA levels in the anterior pituitary gland compared with unstimulated pituitary glands assayed immediately after removal from the pituitary. However, the stimulatory effects were no greater than those seen with medium alone. This suggested that fos expression could be stimulated by local factors either in the pituitary or the medium itself. The second phase of the study focused on pituitary cells plated for 1 hr and then stimulated with EGF and GnRH for 15 min. Dual immunocytochemistry was done to learn which cell types expressed the fos proteins. After 15 min, EGF and GnRH both increased the percentages of fos-bearing cells above levels seen in medium alone. EGF stimulated fos proteins in subsets of FSH, adrenocorticotropin (ACTH), and growth hormone (GH) cells. GnRH increased fos proteins in subsets of ACTH and GH cells. These results suggest that EGF and GnRH may regulate fos expression, but not necessarily in gonadotropes. They also highlight the need for carefully timed experiments because endogenous factors in the pituitary itself may stimulate immediate early gene expression. (J Histochem Cytochem 46: [935][936][937][938][939][940][941][942][943] 1998)

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Section: Effects Of Gnrh On Fos Proteinssupporting

confidence: 85%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 96%

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Regulation of c-fos Expression by EGF and GnRH in Specific Anterior Pituitary Cells from Proestrous Female Rats

Armstrong

Childs

1998

J Histochem Cytochem.

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“…The relative cellular specificity of Egr1 transcription is interesting because it is distinct from other inducible transcription factors such as c-Fos, for example, that is expressed equally in all types of pituitary hormone-producing cells in female rats (Armstrong & Childs 1997). The specific sequences that direct Egr1 expression to pituitary sub-populations are interesting for two reasons.…”

Section: Discussionmentioning

confidence: 99%

Cellular distribution of Egr1 transcription in the male rat pituitary gland

Man

Wells

Carter

2014

Journal of Molecular Endocrinology

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The transcription factor gene Egr1 is necessary for female fertility; EGR1 protein is an established molecular regulator of adult female gonadotroph function where it mediates GNRH-stimulated transcription of the Lhb gene. Recent studies have also implicated pituitary EGR1 in the mediation of other physiological signals indicating an integrative function. However, the role of EGR1 in males is less well defined and this uncertainty is compounded by the absence of cellular expression data in the male pituitary gland. The aim of this study, therefore, was to define the distribution of Egr1 gene expression in the adult male rat pituitary. To further this aim, we have evaluated cellular populations in a transgenic rat model (Egr1-d2EGFP), in which we demonstrate regulated green fluorescent protein (GFP) expression in EGR1C pituitary cells. Cellular filling by GFP enabled morphological and molecular differentiation of different populations of gonadotrophs; Egr1 transcription and LHB were highly co-localised in a major population of large cells but only minimally co-localised in small GFPC cells; the latter cells were shown to be largely (80%) composed of minority populations of GHC somatotrophs (9% of total GHC) and PRLC lactotrophs (3% of total PRLC). Egr1 transcription was not found in TSHC, ACTHC or SOX2C precursor cells and was only minimally co-localised in S-100bC folliculostellate cells. Our demonstration that the Egr1 gene is actively and selectively transcribed in a major sub-population of male LHBC cells indicates a largely conserved role in gonadotroph function and has provided a basis for further defining this role.

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“…The importance of c-fos to the regulation of the ovulatory cycle is suggested by the variation of c-fos expression between the stages of the cycle [11]. However, information on the manner in which c-fos is regulated by peptides, although vital to understanding longer-term gonadotrope control, is limited.…”

Section: Introductionmentioning

confidence: 99%

Regulation of C-fos Protein in Gonadotrope Cells by Oxytocin and Gonadotropin-Releasing Hormone

Abbas¹,

Evans²

2000

Neuroendocrinology

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The integrated regulation of luteinizing hormone (LH) from the anterior pituitary gland is vital to the functioning of the ovulatory cycle in the female and consists of several components acting at different time points. The best-studied is the rapid release of LH elicited by gonadotropin-releasing hormone (GnRH). The so-called primary (immediate early) response genes (PRGs), including c-fos, regulate relatively long-term activities, such as mitosis, protein synthesis, protein release and cell differentiation. Regular ovulatory cycles occur as a result of interaction of several peptide factors including the primary factor, GnRH and oxytocin, although GnRH and oxytocin do not have identical activities. We wished to determine whether oxytocin could mediate changes in expression of c-fos protein and compare its effects with those of GnRH. Anterior pituitary glands were collected from female rats at proestrus and a single-cell suspension prepared. Cells were incubated with oxytocin or GnRH at selected concentrations for various times. C-fos protein was extracted and submitted to Western blot analysis. Other cells were stained immunohistochemically for c-fos and LH following incubation with the peptides and fixation. There was an increase in c-fos protein from 15 to 60 min in Western blots of cells from all incubations. After immunohistochemistry, it was observed that both oxytocin (100 nM) and GnRH (100 nM) increased the percentage of cells that expressed c-fos protein (p < 0.001) and of cells that expressed LH (p < 0.001). The responses to the peptides were concentration dependent. We found that neither all LH-containing cells expressed c-fos, nor all c-fos-containing cells immunostained for LH. The effects of the peptides were not the same. High concentrations of GnRH (1 µM) induced the appearance of a higher percent of LH-containing cells having c-fos than did 10 nM GnRH (p < 0.01), whereas a lower percent of LH-containing cells with c-fos were observed when the oxytocin concentration was raised from 10 nM to 1 µM (p < 0.02). It appears, therefore, that the two peptides have different regulatory effects on LH-containing cells, indicating the possibility of specialized function. The results emphasize the suggestion that stimulation of LH secretion is not the sole index of gonadotrope-directed activity by a peptide. Collectively, these results indicate that the peptides oxytocin and GnRH are able to modulate processes that are associated with longer-term activities of gonadotropes and also demonstrate that specific subpopulations of LH-containing gonadotropes are stimulated to express c-fos.

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Differential Expression of c-fos In Vitro by All Anterior Pituitary Cell Types During the Estrous Cycle: Enhanced Expression by Luteinizing Hormone but Not by Follicle-stimulating Hormone Cells

Cited by 9 publications

References 44 publications

Regulation of c-fos Expression by EGF and GnRH in Specific Anterior Pituitary Cells from Proestrous Female Rats

Regulation of c-fos Expression by EGF and GnRH in Specific Anterior Pituitary Cells from Proestrous Female Rats

Cellular distribution of Egr1 transcription in the male rat pituitary gland

Regulation of C-fos Protein in Gonadotrope Cells by Oxytocin and Gonadotropin-Releasing Hormone

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