scholarly journals The sodium leak channel NALCN encodes the major background sodium ion conductance in murine anterior pituitary cells

2021 ◽  
Author(s):  
Marziyeh Belal ◽  
Mariusz Mucha ◽  
Arnaud Monteil ◽  
Paul G Winyard ◽  
Robert Pawlak ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Anterior Pituitary ◽  
Hormone Secretion ◽  
Pituitary Cell ◽  
Resting Membrane Potential ◽  
Pituitary Cells ◽  
Firing Activity ◽  
Cell Excitability ◽  
Leak Channel ◽  
Anterior Pituitary Cells

The pituitary gland, the so-called master gland produces and secretes a variety of hormones essential for regulating growth and development, metabolic homeostasis, reproduction, and the stress response. The interplay between the brain and peripheral feedback signals controls hormone secretion from pituitary cells by regulating the properties of ion channels, and in turn, cell excitability. Endocrine anterior pituitary cells fire spontaneous action potentials to regulate their intracellular calcium level and eventually hormone secretion. However, the molecular identity of the non-selective cationic leak channel involved in maintaining the resting membrane potential at the firing threshold remained unknown. Here, we show that the sodium leak channel NALCN, known to modulate neuronal excitability, also regulates excitability in murine anterior pituitary cells. Using viral transduction combined with electrophysiology and calcium imaging we show that NALCN encodes the major Na+ leak conductance which tunes the resting membrane potential close to firing threshold to sustain the intrinsically-regulated firing in endocrine pituitary cells. Genetic interruption of NALCN channel activity, hyperpolarised the membrane potential drastically and stopped the firing activity, and consequently abolished the cytosolic calcium oscillations. Moreover, we found that NALCN conductance forms a very small fraction of the total cell conductance yet has a profound impact on modulating pituitary cell excitability. Taken together, our results demonstrate that, NALCN is a crucial regulator of pituitary cell excitability and supports spontaneous firing activity to consequently regulate hormonal secretion. Our results suggest that receptor-mediated and potentially circadian changes in NALCN conductance can powerfully affect the pituitary activity and hormone secretion.

Control of secretion in anterior pituitary cells--linking ion channels, messengers and exocytosis

1988 ◽  
Vol 139 (1) ◽  
pp. 287-316
Author(s):  
W. T. Mason ◽  
S. R. Rawlings ◽  
P. Cobbett ◽  
S. K. Sikdar ◽  
R. Zorec ◽  
...  
Keyword(s):  
Ion Channels ◽  
Intracellular Calcium ◽  
Anterior Pituitary ◽  
Hormone Secretion ◽  
Cell Types ◽  
Pituitary Cell ◽  
Pituitary Cells ◽  
Calcium Activity ◽  
Anterior Pituitary Cells ◽  
Voltage Dependent

Normal anterior pituitary cells, in their diversity and heterogeneity, provide a rich source of models for secretory function. However, until recently they have largely been neglected in favour of neoplastic, clonal tumour cell lines of pituitary origin, which have enabled a number of studies on supposedly homogeneous cell types. Because many of these lines appear to lack key peptide and neurotransmitter receptors, as well as being degranulated with accompanying abnormal levels of secretion, we have developed a range of normal primary anterior pituitary cell cultures using dispersion and enrichment techniques. By studying lactotrophs, somatotrophs and gonadotrophs we have revealed a number of possible transduction mechanisms by which receptors for hypothalamic peptides and neurotransmitters may control secretion. In particular, the transduction events controlling secretion from pituitary cells may differ fundamentally from those found in other cell types. Patch-clamp recordings in these various pituitary cell preparations have revealed substantial populations of voltage-dependent Na+, Ca2+ and K+ channels which may support action potentials in these cells. Although activation of these channels may gate Ca2+ entry to the cells under some conditions, our evidence taken with that of other laboratories suggests that peptide-receptor interactions leading to hormone secretion occur independently of significant membrane depolarization. Rather, secretion of hormone and rises in intracellular calcium measured with new probes for intracellular calcium activity, can occur in response to hypothalamic peptide activation in the absence of substantial changes in membrane potential. These changes in intracellular calcium activity almost certainly depend on both intracellular and extracellular calcium sources. In addition, strong evidence of a role for multiple intracellular receptors and modulators in the secretory event suggests we should consider the plasma membrane channels important for regulation of hormone secretion to be predominantly agonist-activated, rather than of the more conventional voltage-dependent type. Likewise, evidence from new methods for recording single ion channels suggests the existence of intracellular sites for channel modulation, implying they too may play an important role in secretory regulation. We shall consider new data and new technology which we hope will provide key answers to the many intriguing questions surrounding the control of pituitary hormone secretion. We shall highlight our work with recordings of single ion channels activated by peptides, and recent experiments using imaging of intracellular ionized free calcium.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of osmotic shrinkage on voltage-gated Ca2+ channel currents in rat anterior pituitary cells

2006 ◽  
Vol 290 (1) ◽  
pp. C222-C232 ◽  
Author(s):  
Shlomo Ben-Tabou De-Leon ◽  
Galia Ben-Zeev ◽  
Itzhak Nussinovitch
Keyword(s):  
Anterior Pituitary ◽  
Single Channel ◽  
Hormone Secretion ◽  
Reversal Potential ◽  
Pituitary Cell ◽  
Pituitary Cells ◽  
Anterior Pituitary Cells ◽  
Access Resistance ◽  
Channel Currents ◽  
Percent Decrease

Increased extracellular osmolarity ([Os]e) suppresses stimulated hormone secretion from anterior pituitary cells. Ca2+ influx may mediate this effect. We show that increase in [Os]e (by 18–125%) differentially suppresses L-type and T-type Ca2+ channel currents ( IL and IT, respectively); IL was more sensitive than IT. Hyperosmotic suppression of IL depended on the magnitude of increase in [Os]e and was correlated with the percent decrease in pituitary cell volume, suggesting that pituitary cell shrinkage can modulate L-type currents. The hyperosmotic suppression of IL and IT persisted after incubation of pituitary cells either with the actin-disrupter cytochalasin D or with the actin stabilizer phalloidin, suggesting that the actin cytoskeleton is not involved in this modulation. The hyperosmotic suppression of Ca2+ influx was not correlated with changes in reversal potential, membrane capacitance, and access resistance. Together, these results suggest that the hyperosmotic suppression of Ca2+ influx involves Ca2+ channel proteins. We therefore recorded the activity of L-type Ca2+ channels from cell-attached patches while exposing the cell outside the patch pipette to hyperosmotic media. Increased [Os]e reduced the activity of Ca2+ channels but did not change single-channel conductance. This hyperosmotic suppression of Ca2+ currents may therefore contribute to the previously reported hyperosmotic suppression of hormone secretion.

GRF elevates cytosolic free calcium concentration in rat anterior pituitary cells

1987 ◽  
Vol 253 (5) ◽  
pp. E591-E594
Author(s):  
C. Schofl ◽  
J. Sandow ◽  
W. Knepel
Keyword(s):  
Growth Hormone ◽  
Anterior Pituitary ◽  
Calcium Concentration ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Free Calcium ◽  
Pituitary Cells ◽  
Maximal Increase ◽  
Anterior Pituitary Cells ◽  
Free Calcium Concentration

The effect of human growth hormone-releasing factor (GRF) on intracellular free calcium concentration ([Ca2+]i) was examined in rat anterior pituitary cells. The [Ca2+]i was monitored directly by means of the intracellularly trapped fluorescent indicator, fura-2. GRF rapidly elevated [Ca2+]i, reaching a new plateau within approximately 30 s. The half-maximally effective concentration of GRF was approximately 130 pM. GRF produced a maximal increase in [Ca2+]i by approximately 120 nM. The GRF (2 nM)-induced elevation of [Ca2+]i was abolished by removal of extracellular calcium (Ca2+ omitted, 2 mM EGTA). The GRF (2 nM)-caused rise in [Ca2+]i was largely reduced in the presence of the calcium channel blockers Mg2+ (31.2 mM) or nifedipine (1 microM). An increase in [Ca2+]i by approximately 60 nM was elicited by the addition of prostaglandin E2 (1 microM), which can stimulate growth hormone secretion independent of GRF receptors. These data indicate that GRF elevates the [Ca2+]i, possibly in somatotrophs; this GRF-induced increase in [Ca2+]i may depend on an influx of extracellular Ca2+, largely through Mg2+- and nifedipine-sensitive calcium channels.

scholarly journals Leptin and Leptin Receptor Expression in Normal and Neoplastic Human Pituitary: Evidence of a Regulatory Role for Leptin on Pituitary Cell Proliferation1

1999 ◽  
Vol 84 (8) ◽  
pp. 2903-2911 ◽  
Author(s):  
Long Jin ◽  
Bartolome G. Burguera ◽  
Marta E. Couce ◽  
Bernd W. Scheithauer ◽  
Jesse Lamsan ◽  
...  
Keyword(s):  
Anterior Pituitary ◽  
Leptin Receptor ◽  
Pituitary Cell ◽  
Receptor Expression ◽  
Receptor Protein ◽  
Pituitary Cells ◽  
Double Labeling ◽  
Messenger Ribonucleic Acid ◽  
Anterior Pituitary Cell ◽  
Anterior Pituitary Cells

Leptin is a circulating hormone secreted by adipose and a few other tissues. The leptin receptor consists of a single transmembrane-spanning polypeptide that is present as a long physiologically important form as well as in several short isoforms. Recent studies have suggested that the anterior pituitary may have a role in the regulatory effects of leptin in animal models. To test this possibility in human pituitaries, we examined the expression of leptin and OB-R in normal and neoplastic pituitaries, and the possible functions of leptin in the pituitary were also analyzed. Leptin was present in 20–25% of anterior pituitary cells and was expressed in most normal anterior pituitary cells, including ACTH (70% of ACTH cells), GH (21%), FSH (33%), LH (29%), TSH (32%), and folliculo-stellate cells (64%), but was colocalized with very few PRL cells (3%), as detected by double labeling immunohistochemistry with two different antileptin antibodies. In addition, leptin expression was detected by RT-PCR in some pituitary tumors, including ACTH (three of four), GH (one of four), null cells (two of four), and gonadotroph (one of four) tumors as well as in normal pituitary. Immunohistochemical staining showed greater immunoreactivity for leptin in normal pituitaries compared to adenomas. Treatment of an immortalized cultured anterior pituitary cell line, HP75, with leptin stimulated pancreastatin secretion in vitro. Leptin also inhibited cell growth in the human HP75 and in the rat pituitary GH3 cell lines. Both long (OB-Rb) and common (OB-Ra) forms of the leptin receptor messenger ribonucleic acid and leptin receptor protein were expressed in normal and neoplastic anterior pituitary cells. These findings show for the first time that leptin is expressed by most human anterior pituitary cell types and that there is decreased leptin protein immunoreactivity in pituitary adenomas compared to that in normal pituitary tissues. We also show that OB-Rb is widely expressed by normal and neoplastic anterior pituitary cells, implicating an autocrine/paracrine loop in the production and regulation of leptin in the pituitary.

Mastoparan, a wasp venom peptide, stimulates release of prolactin from cultured rat anterior pituitary cells

1994 ◽  
Vol 142 (1) ◽  
pp. 9-18 ◽  
Author(s):  
S E Mau ◽  
M R Witt ◽  
H Vilhardt
Keyword(s):  
Protein Kinase ◽  
Cell Cultures ◽  
Anterior Pituitary ◽  
Inositol Phosphates ◽  
Pituitary Cell ◽  
Secretory Process ◽  
Protein Kinase Activity ◽  
Pituitary Cells ◽  
Anterior Pituitary Cells ◽  
Intracellular Ca

Abstract Studies have shown that mastoparan and other amphiphilic peptides induce exocytosis of hormones from anterior pituitary cells. We have studied the effect of mastoparan on the secretion of prolactin from cultured rat anterior pituitary cells and on the concomitant functional status of signal-transducing pathways in lactotroph-enriched cell cultures. Mastoparan stimulation of prolactin secretion was dose-dependent, time-dependent, reversible and required the presence of calcium. Pretreatment of pituitary cell cultures with cholera and pertussis toxin had no effect on the secretory response, whereas encapsulation of guanosine 5-[β-thio]diphosphate (GDP-β-S) by reversible electropermeabilization inhibited mastoparan-stimulated secretion. Incubation of mastoparan with myo[3H]inositol-labelled lactotroph-enriched anterior pituitary cell cultures resulted in increased formation of inositol phosphates compared with control cells, and encapsulation of GDP-β-S blocked mastoparan-induced inositol lipid hydrolysis. Mastoparan caused translocation of protein kinase C activity from a soluble to a membrane-attached form. Mastoparan was able to increase the intracellular Ca2+ concentration in Fura-2-loaded individual lactotrophs. Omission of Ca2+ from the extracellular medium did not change the Ca2+ response in lactotrophs when stimulated with mastoparan. On the basis of these results it is concluded that mastoparan-induced release of prolactin is preceded by activation of the inositol(1,4,5)trisphosphate/diacylglycerol pathway with resulting translocation of protein kinase activity and increment in intracellular Ca2+. However, other signal-transducing pathways may be involved in the secretory process. Journal of Endocrinology (1994) 142, 9–18

scholarly journals Expression of Transgenes in Normal and Neoplastic Anterior Pituitary Cells Using Recombinant Adenoviruses: Long Term Expression, Cell Cycle Dependency, and Effects on Hormone Secretion*

Endocrinology ◽  
1997 ◽  
Vol 138 (5) ◽  
pp. 2184-2194 ◽  
Author(s):  
Maria G. Castro ◽  
Rodolfo G. Goya ◽  
Yolanda E. Sosa ◽  
Joanna Rowe ◽  
Adriana Larregina ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Anterior Pituitary ◽  
Hormone Secretion ◽  
Pituitary Cells ◽  
Anterior Pituitary Cells
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