Regulation of Growth Hormone mRNA and Pro-Opiomelanocortin mRNA Levels by Cyclic AMP in Rat Anterior Pituitary Cells in Culture

Simard, Jacques; Labrie, Fernand; Gossard, Françis

doi:10.1089/dna.1986.5.263

Cited by 35 publications

(9 citation statements)

References 31 publications

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“…However, because the β-actin mRNA level was decreased by 10 m M 8Br-cAMP (data not shown), the increase by 10 m M 8Br-cAMP was not a valid measurement. Previous studies have shown that treatment of various tissues (including rat anterior pituitaries) for 20–72 h with 1–3 m M 8Br-cAMP did not change β-actin mRNA levels [19, 26, 27, 28, 29]. However, higher concentrations of 8Br-cAMP (5–10 m M ) increased β-actin mRNA levels in human hepatoblastoma cell lines [30], and decreased β-actin mRNA levels in rat osteoblastic cells [31].…”

Section: Resultsmentioning

confidence: 99%

Expression of the L-Type Ca<sup>2+</sup> Channel in AtT-20 Cells Is Regulated by Cyclic AMP

Xie¹,

Nagle²,

Childs³

et al. 1999

Neuroendocrinology

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Activation of adenylyl cyclase by corticotropin-releasing hormone (CRH) stimulates secretion of adrenocorticotropin (ACTH) in rat anterior pituitary corticotropes and in the murine AtT-20 cell line. The stimulation of secretion is mediated by cAMP and is largely dependent on Ca²⁺ influx through voltage-gated L-type Ca²⁺ channels. To investigate whether CRH and cAMP also increase expression of the L-type Ca²⁺ channel in AtT-20 cells, an RNase protection assay was used to measure the α_1C mRNA that encodes the pore-forming subunit of the L-type Ca²⁺ channel. The α_1C mRNA level was measured by autoradiographic densitometry and normalized to the β-actin mRNA level in the same sample. The α_1C mRNA was not changed by 24-hour treatment with CRH (10–500 nM). A 24-hour treatment with 1 mM 8Br-cAMP significantly increased the α_1C mRNA by 40% over its control. The stimulatory effect was blocked by 2 µM actinomycin D and was, therefore, dependent on gene transcription. The measured half-life of the α_1C mRNA, after inhibition of transcription, was 4.7 ± 0.3 h in control and 5.2 ± 0.6 h in the presence of 8Br-cAMP. Thus the 8Br-cAMP- induced increase in α_1C mRNA could be due to an increase in α_1C gene transcription or to a transcriptionally regulated increase in a protein that helps to stabilize α_1C mRNA. Finally, to determine if the increased mRNA was followed by an increase in production of L-type Ca²⁺ channels, the binding of [³H]PN200-110 to Ca²⁺ channel proteins was assayed in AtT-20 membrane fragments. 8Br-cAMP increased [³H]PN200-110 binding sites by 32% (B_max 36.0 ± 1.2 fmol/mg protein in control vs. 47.4 ± 3.2 fmol/mg protein in 8Br-cAMP-treated cells) but did not change the K_d. These studies show that both α_1C mRNA and L-type Ca²⁺ channel protein are increased in AtT-20 cells by cAMP.

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Section: Resultsmentioning

confidence: 99%

Expression of the L-Type Ca<sup>2+</sup> Channel in AtT-20 Cells Is Regulated by Cyclic AMP

Xie¹,

Nagle²,

Childs³

et al. 1999

Neuroendocrinology

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“…2). Previous studies have shown that although somatostatin inhibits growth hormone release by > 90% (33), it has no effect on the levels of growth hormone mRNA (34,35) or on growth hormone gene transcription (36). However, other regulatory peptides have been shown to modulate target cell function at several levels.…”

Section: Discussionmentioning

confidence: 99%

Inhibition of gastrin gene expression by somatostatin.

1989

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Previous studies performed in this laboratory have demonstrated somatostatin-containing cells in close proximity to gastrin cells in antral mucosa and have shown that somatostatin exerts a local regulatory effect on gastrin release. The present studies were directed to determine whether the effects of somatostatin on the antral gastrin cell involve pretranslational events. The effects of somatostatin on gastrin mRNA were determined by dot blot hybridization using a gastrin antisense RNA probe derived from human gastrin cDNA. Inclusion of somatostatin in the incubation medium caused a dosedependent inhibition of steady-state gastrin mRNA. Conversely, when antral somatostatin was neutralized by the addition of specific somatostatin antibodies to the incubation medium, gastrin mRNA levels increased by 116±31% over control values (P < 0.01). Northern blot hybridization of total antral RNA demonstrated a single major band with a molecular size of -620 nucleotides, closely matching the predicted size of gastrin mRNA. The effect of somatostatin on the rate of gastrin gene transcription was examined using nuclear run-off transcription assays. Inclusion of antibodies to somatostatin in the incubation medium resulted in a 33.8±3.3% increase in gastrin gene transcriptional activity (P < 0.01). These studies indicate that, in addition to its established effect on peptide release, somatostatin exerts inhibitory effects on antral gastrin cells at the pretranslational level. Although this inhibition appears to occur in part at the gene transcriptional level, the results also indicate that somatostatin may affect posttranscriptional processing of gastrin mRNA.

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“…SRIF did not affect GH mRNA expression, but did suppress intracellular GH protein levels and decreased GH secretion in primary rat anterior pituitary cells (Simard et al 1986). Similarly, SRIF inhibited GH secretion without affecting GH mRNA expression in primary human GH-secreting tumors cells (Davis et al 1989).…”

Section: Gh Secretionmentioning

confidence: 98%

“…While direct inhibition of pituitary hormone transcription has yet to be definitively associated with SRIF signaling, as some studies demonstrate a SRIF-dependent decrease in GH mRNA levels (Sugihara et al 1993, Tsukamoto et al 1994, Acunzo et al 2008) others describe no change (Simard et al 1986, Davis et al 1989, Namba et al 1989, Tanner et al 1990, Gruszka et al 2007, and some even demonstrate upregulation of gene expression possibly reflecting a GH-rebound effect after termination of SRIF treatment; the latter exemplifies the importance of outcome measurement timing. SRIF did not affect GH mRNA expression, but did suppress intracellular GH protein levels and decreased GH secretion in primary rat anterior pituitary cells (Simard et al 1986).…”

Section: Gh Secretionmentioning

confidence: 99%

Somatostatin system: molecular mechanisms regulating anterior pituitary hormones

Eigler¹,

Ben-Shlomo²

2014

Journal of Molecular Endocrinology

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The somatostatin (SRIF) system, which includes the SRIF ligand and receptors, regulates anterior pituitary gland function, mainly inhibiting hormone secretion and to some extent pituitary tumor cell growth. SRIF-14 via its cognate G-protein-coupled receptors (subtypes 1-5) activates multiple cellular signaling pathways including adenylate cyclase/cAMP, MAPK, ion channel-dependent pathways, and others. In addition, recent data have suggested SRIF-independent constitutive SRIF receptor activity responsible for GH and ACTH inhibition in vitro. This review summarizes current knowledge on ligand-dependent and independent SRIF receptor molecular and functional effects on hormone-secreting cells in the anterior pituitary gland.

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Regulation of Growth Hormone mRNA and Pro-Opiomelanocortin mRNA Levels by Cyclic AMP in Rat Anterior Pituitary Cells in Culture

Cited by 35 publications

References 31 publications

Expression of the L-Type Ca<sup>2+</sup> Channel in AtT-20 Cells Is Regulated by Cyclic AMP

Expression of the L-Type Ca<sup>2+</sup> Channel in AtT-20 Cells Is Regulated by Cyclic AMP

Inhibition of gastrin gene expression by somatostatin.

Somatostatin system: molecular mechanisms regulating anterior pituitary hormones

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