Influence of Calcium Ions on Proopiomelanocortin mRNA Levels in Clonal Anterior Pituitary Cells

1988 ◽  
Vol 47 (1) ◽  
pp. 32-37 ◽  
Author(s):  
Gerhard Von Dreden ◽  
Jean-Philippe Loeffler ◽  
Cornelia Grimm ◽  
Volker Höllt
Keyword(s):  
Calcium Ions ◽  
Anterior Pituitary ◽  
Pituitary Cells ◽  
Mrna Levels ◽  
Anterior Pituitary Cells

Effects of vasopressin and elimination of corticotropin-releasing hormone-target cells on pro-opiomelanocortin mRNA levels and adrenocorticotropin secretion in ovine anterior pituitary cells

1997 ◽  
Vol 154 (1) ◽  
pp. 139-147 ◽  
Author(s):  
S A van de Pavert ◽  
I J Clarke ◽  
A Rao ◽  
K E Vrana ◽  
J Schwartz
Keyword(s):  
Protein Kinase C ◽  
Steady State ◽  
Anterior Pituitary ◽  
Target Cells ◽  
Pituitary Cells ◽  
Mrna Levels ◽  
Acth Secretion ◽  
Kinase C ◽  
Pomc Mrna ◽  
Anterior Pituitary Cells

Abstract Although arginine-vasopressin (AVP) is reported to produce greater ACTH biosynthetic and secretory responses than does corticotropin-releasing hormone (CRH) in sheep anterior pituitary cells, neither factor appears to increase pro-opiomelanocortin (POMC) mRNA levels, as does CRH in the cells of some other species. Since only a fraction of cells that express POMC mRNA may be able to respond to AVP, the aim of this study was to further delineate the regulation of POMC mRNA in ovine anterior pituitary corticotrophs, as a whole and in functional subpopulations of corticotrophs. We measured the effects of AVP, CRH or activation of protein kinase C by phorbol myristate acetate (PMA) in cultured cells. We compared responses in intact populations with those of cultures from which CRH-target cells were pharmacologically eliminated. Dissociated adult ovine anterior pituitary cells were cultured overnight, treated with either vehicle (intact) or a CRH-toxin conjugate that specifically eliminates CRH-target cells (CRH-target-depleted), washed, returned to culture and subsequently challenged with vehicle, AVP (100 nm), CRH (10 nm) or PMA (1 μm) for 5 h. The media were assayed for ACTH by RIA and the cells for POMC mRNA by Northern blot analysis. In intact populations, AVP and CRH increased ACTH secretion from 6·5 ±1·2 to 216 ±22 and 81 ± 14 ng/well respectively, but only AVP caused an increase in steady-state POMC mRNA levels (+48 ± 10%). Direct activation of protein kinase C with PMA mimicked the effect of AVP on ACTH secretion (318 ± 16 ng/well), but did not alter POMC mRNA levels. In CRH-target-depleted populations, control ACTH secretion (11 ± 3 ng/well) and POMC mRNA (+69 ±7%) were elevated, compared with intact populations. AVP (55 ± 8 ng/well) and PMA (120 ± 17 ng/well), but not CRH, increased ACTH secretion; POMC mRNA was not significantly elevated by any of the treatments. Taken together, these data provide further support for the notion of dissociation between secretion of ACTH and expression of POMC mRNA, and demonstrate that AVP increases steady-state POMC mRNA levels in ovine anterior pituitary cells. The data are also consistent with the concept that complex interactions, possibly including those between cells, influence ACTH secretion and steady-state POMC mRNA levels. Journal of Endocrinology (1997) 154, 139–147

scholarly journals Cocaine- and Amphetamine-Regulated Transcript Activates the Hypothalamic-Pituitary-Adrenal Axis through a Corticotropin-Releasing Factor Receptor-Dependent Mechanism

Endocrinology ◽  
2004 ◽  
Vol 145 (11) ◽  
pp. 5202-5209 ◽  
Author(s):  
Sean M. Smith ◽  
Joan M. Vaughan ◽  
Cynthia J. Donaldson ◽  
Jean Rivier ◽  
Chien Li ◽  
...  
Keyword(s):  
Hpa Axis ◽  
Anterior Pituitary ◽  
Corticotropin Releasing Factor ◽  
Pituitary Cells ◽  
Mrna Levels ◽  
Hypothalamic Pituitary Adrenal ◽  
Anterior Pituitary Cells ◽  
Circulating Levels ◽  
Dependent Mechanism ◽  
Acth Release

Abstract Cocaine- and amphetamine-regulated transcript (CART) is a highly expressed hypothalamic transcript that is concentrated in areas associated with the stress response. There is evidence for a role of CART in the regulation of the hypothalamic-pituitary-adrenal (HPA) axis. However, it is not clear whether CART regulates activity of the HPA axis by directly stimulating ACTH release from pituitary corticotropes or through interaction with hypothalamic factors. To address this issue, the effects of central and peripheral administration of CART on the HPA axis were compared. Central administration of CART(55–102) (1 μg) significantly increased circulating levels of ACTH (481 ± 122 vs. 93 ± 14 pg/ml; CART vs. vehicle) and corticosterone (460 ± 29 vs. 179 ± 62 ng/ml; CART vs. vehicle). In contrast, iv injection of CART(55–102) (0.09-9.0 nmol/kg) did not significantly affect circulating levels of ACTH or corticosterone. The corticotropin-releasing factor (CRF) receptor antagonist Astressin B was used to determine whether CART(55–102) elicits ACTH secretion via a CRF receptor-dependent mechanism. Injection of Astressin B (50 μg/kg, iv) inhibited CART(55–102)-induced ACTH and corticosterone responses. The effects of CART(55–102) on CRF and arginine vasopressin (AVP) expression were also examined in static hypothalamic explants. RT-PCR analysis revealed a significant up-regulation of CRF and AVP mRNA levels after CART(55–102) (10 nm and 1 μm) treatment. Last, the effects of CART(55–102) on CRF- and AVP-mediated ACTH release was investigated in dispersed rat anterior pituitary cells. Incubation of CART(55–102) (10–100 nm) did not significantly affect ACTH release from anterior pituitary cells. Findings from the present study suggest that CART regulates activity of the HPA axis through a CRF-dependent central mechanism and not by means of direct interaction with pituitary corticotropes.

scholarly journals Estradiol differentially modulates the exocytotic proteins SNAP-25 and munc-18 in pituitary gonadotrophs

2007 ◽  
Vol 38 (2) ◽  
pp. 305-314 ◽  
Author(s):  
Jürgen M Weiss ◽  
Heike Hüller ◽  
Stephan Polack ◽  
Michael Friedrich ◽  
Klaus Diedrich ◽  
...  
Keyword(s):  
Gene Expression ◽  
Anterior Pituitary ◽  
Neuroendocrine Cells ◽  
Pituitary Cells ◽  
Mrna Levels ◽  
Rt Pcr ◽  
Estradiol Treatment ◽  
Anterior Pituitary Cells ◽  
Lh Secretion

Long-term treatment with estradiol increases LH secretion from female gonadotrophs. The mechanisms are not fully clarified yet. Our previous data indicated that sexual steroids might affect late steps in GnRH signal transduction such as exocytosis. The secretion of hormones from neuroendocrine cells requires the merger of secretory vesicles with the plasma membrane. This regulated exocytosis is mediated by specific proteins, which are present in the pituitary gland. Here, we examined whether two of these crucial exocytotic proteins, SNAP-25 and munc-18, are affected by estradiol in female gonadotrophs. Female rat anterior pituitary cells and αT3-1 cells, derived from a murine immortalized gonadotroph cell line, were treated with 100 pM estradiol for 48 h. LH secretion of anterior pituitary cells, additionally stimulated with eight consecutive pulses of 1 nM GnRH for 15 min at an interval of 1 h, was determined by RIA. Gene expression was measured by quantitative RT-PCR and protein expression by immunoblotting. Additionally, quantitative RT-PCR was performed in single rat gonadotrophs to ascribe effects exclusively to intact gonadotrophs. Pulsatile GnRH enhanced the mRNA expression of SNAP-25 and munc-18 in accordance with the LH secretory response with the greatest increase at the third pulse of GnRH. Estradiol treatment further increased GnRH-induced LH secretion at all GnRH pulses. SNAP-25 gene expression was significantly decreased at the fifth GnRH pulse and unaffected at basal after 48 h of estradiol treatment. In contrast, munc-18 mRNA levels were not significantly affected by estradiol at different GnRH-pulses in mixed anterior pituitary cells, whereas munc-18 gene expression was significantly increased at basal. In αT3-1 cells and single gonadotrophs, long-term estradiol treatment significantly reduced SNAP-25 protein and gene expression. In contrast, the protein and gene expression of munc-18 was significantly enhanced in both αT3-1 cells and single gonadotrophs. In conclusion, munc-18 and SNAP-25 were oppositionally influenced by estradiol. The results suggest that estradiol modulates the expression of exocytotic proteins in gonadotrophs and thus affects LH secretion.

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