Arachidonate 12-lipoxygenase in porcine anterior pituitary cells: its localization and possible function in gonadotrophs

1996 ◽  
Vol 148 (1) ◽  
pp. 33-41 ◽  
Author(s):  
H Ikawa ◽  
K Yamamoto ◽  
Y Takahashi ◽  
N Ueda ◽  
Y Hayashi ◽  
...  
Keyword(s):  
Anterior Pituitary ◽  
Nordihydroguaiaretic Acid ◽  
Pituitary Hormones ◽  
Pituitary Hormone ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
Lipoxygenase Inhibitor ◽  
Anterior Pituitary Cells ◽  
Significant Stimulation ◽  
12 Lipoxygenase

Abstract Arachidonate 12-lipoxygenase, which oxygenates positions 12 and 13 of arachidonic and linoleic acids, is present in porcine anterior pituitary cells. Colocalization of the 12-lipoxygenase with various pituitary hormones was examined by immunohistochemical double-staining using antibodies against 12-lipoxygenase and various anterior pituitary hormones. Under light microscopy, approximately 7% of the cells producing luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were positive for 12-lipoxygenase, whereas the enzyme was detected in less than 2% of the cells producing thyrotrophin, prolactin, growth hormone (GH), and adrenocorticotrophin. In an attempt to examine the participation of 12-lipoxygenase metabolites in pituitary hormone release, we incubated the primary culture of porcine anterior pituitary cells with 12-hydroperoxy-arachidonic acid or 13-hydroperoxy-linoleic acid. Significant stimulation of LH and FSH release by these hydroperoxides was observed at 10 μm in a time-dependent manner. At doses around 10 μm these compounds produced responses of similar magnitude to 1 nm gonadotrophin-releasing hormone (GnRH), but higher concentrations (30 μm) of the compounds were required for GH release. In contrast, 12-hydroxy-arachidonic and 13-hydroxy-linoleic acids were almost ineffective. Furthermore, the gonadotrophin release by 1 nm GnRH was inhibited by nordihydroguaiaretic acid (a lipoxygenase inhibitor) with an IC50 of about 5 μm. Thus, the hydroperoxy (but not hydroxy) products of 12-lipoxygenase may be involved in the release of pituitary hormones especially LH and FSH. Journal of Endocrinology (1996) 148, 33–41

Tyrosine kinase inhibitors enhance GHRH-stimulated cAMP accumulation and GH release in rat anterior pituitary cells

1997 ◽  
Vol 152 (2) ◽  
pp. 193-199 ◽  
Author(s):  
T Ogiwara ◽  
C L Chik ◽  
A K Ho
Keyword(s):  
Tyrosine Kinase ◽  
Cholera Toxin ◽  
Tyrosine Kinase Inhibitors ◽  
Anterior Pituitary ◽  
Kinase Inhibitors ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
Camp Accumulation ◽  
Anterior Pituitary Cells ◽  
Site Of Action

Abstract In this study, the role of tyrosine phosphorylation in agonist-stimulated cAMP accumulation and GH release in rat anterior pituitary cells was investigated. It was found that genistein, a tyrosine kinase inhibitor, while having no effect on its own, potentiated GHRH-stimulated cAMP accumulation in a concentration-dependent manner. In comparison, daidzein, an inactive analogue of genistein, was ineffective and vanadate, a phosphotyrosine phosphatase inhibitor, reduced GHRH-stimulated cAMP accumulation. Additional structurally unrelated tyrosine kinase inhibitors, erbstatin and tyrphostins, also potentiated GHRH-stimulated cAMP accumulation. To determine the site of action of the tyrosine kinase inhibitors, pituitary adenylate cyclase-activating polypeptide (PACAP), cholera toxin and forskolin were used to increase cAMP accumulation. Genistein enhanced the PACAP-, cholera toxin- or forskolin-stimulated cAMP accumulation, suggesting that the site of action is at the post-receptor level. However, when the phosphodiesterase was inhibited by isobutylmethylxanthine, genistein did not potentiate and vanadate did not inhibit GHRH-stimulated cAMP accumulation, indicating that phosphodiesterase is a probable site of action for the inhibitor. Genistein and erbstatin also enhanced GHRH-stimulated GH release and the effect of vanadate was inhibitory. These results indicate that tyrosine kinase inhibitors enhance cAMP accumulation through their action on phosphodiesterase activity in rat anterior pituitary cells and the tyrosine kinase pathway appears to be involved in the control of GH release. Journal of Endocrinology (1997) 152, 193–199

Reserpine is a calcium channel antagonist in normal and GH3 rat pituitary cells

1985 ◽  
Vol 248 (1) ◽  
pp. E15-E19
Author(s):  
I. S. Login ◽  
A. M. Judd ◽  
M. J. Cronin ◽  
T. Yasumoto ◽  
R. M. MacLeod
Keyword(s):  
Calcium Channel ◽  
Calcium Channel Antagonist ◽  
Anterior Pituitary ◽  
Calcium Uptake ◽  
Calcium Ionophore ◽  
Gh3 Cells ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Anterior Pituitary Cells

Reserpine exerts direct effects on several tissues, including inhibition of hormone release from rat anterior pituitary cells. To test the hypothesis that reserpine may be acting as a calcium channel antagonist, normal or GH3 rat anterior pituitary cells were preincubated in reserpine or the conventional calcium channel blocker, D-600, followed by exposure to 45Ca2+ together with stimulants of calcium uptake: maitotoxin, a potent calcium channel activator; A23187, a calcium ionophore; or 50 mMK+. After incubation, the cells were harvested by vacuum filtration and cell-associated radioactivity determined. In normal cells, reserpine blocked both basal and K+-stimulated calcium uptake. Reserpine selectively blocked maitotoxin but not A23187-induced calcium uptake. In GH3 cells 9 microM reserpine and 30 microM D-600 were equally effective in blocking maitotoxin-stimulated calcium uptake. Reserpine appears to block voltage-dependent calcium channels in pituitary cells in a concentration-dependent manner but not calcium uptake caused nonspecifically by A23187.

Blockage of K+ channels reverses the inhibitory action of atriopeptin on secretagogue-stimulated ACTH release by perifused isolated rat anterior pituitary cells

1990 ◽  
Vol 126 (2) ◽  
pp. 183-191 ◽  
Author(s):  
F. A. Antoni ◽  
G. Dayanithi
Keyword(s):  
Anterior Pituitary ◽  
Inhibitory Action ◽  
Calcium Ionophore ◽  
Delayed Rectifier ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
Acth Secretion ◽  
Anterior Pituitary Cells ◽  
Isolated Rat ◽  
Acth Release

ABSTRACT The aim of the present study was to investigate how atriopeptin inhibits secretagogue-stimulated ACTH secretion in vitro. Perifused isolated rat anterior pituitary cells were used throughout; the ACTH content of the perifusate was measured by radioimmunoassy. In the presence of a constant (0·05 nmol/l) concentration of 41-residue corticotrophin-releasing factor (CRF), arginine vasopressin (AVP; 0·05–50 nmol/l) stimulated ACTH secretion in a concentration-dependent manner, the combination of 0·05 nmol CRF/l and 0·5 nmol AVP/l (CRF/AVP) stimulated ACTH release to six- to eightfold above baseline. The effect of CRF/AVP was not modified by tetrodotoxin, but was abolished by CoCl2 and reduced to about 70% of the control stimulus by nifedipine. Application of 103–126 residue atriopeptin for 10 min before and 2·5 min during the CRF/AVP stimulus strongly suppressed the evoked release of ACTH, the maximal inhibition was 75–90% at 10 nmol atriopeptin/l. The calcium ionophore ionomycin (200 nmol/l) reversed the effect of atriopeptin while it had no secretagogue activity of its own, and did not enhance the response to CRF/AVP. A variety of blockers of K+ channels, 4-amino pyridine, tetraethylammonium, apamine, quinine, but not tolbutamide, effectively antagonized the inhibitory action of atriopeptin (10 nmol/l). None of these drugs altered ACTH release evoked by CRF/AVP. In concentration–response experiments, the half effective concentration of 4-aminopyridine and tetraethyl-ammonium were around 1 mmol/l and 10 nmol/l for apamine. Finally, tetraethylammonium and apamine also antagonized the inhibition of CRF/AVP-evoked ACTH release by 8-Br-cGMP. These data suggest that (1) at least two types of K+ channels, a delayed rectifier and the apamine-sensitive Ca2+-activated channel, are functionally important in pituitary corticotroph cells; (2) atriopeptin inhibits CRF/AVP-stimulated ACTH secretion by hyperpolarizing the plasma membrane and thus reducing the uptake of Ca2+ into the cells; (3) cGMP is the intracellular mediator of the action of atriopeptin on corticotroph cells. Journal of Endocrinology (1990) 126, 183–191

GRF increases release of growth hormone and arachidonate from anterior pituitary cells

1985 ◽  
Vol 248 (4) ◽  
pp. E438-E442
Author(s):  
A. M. Judd ◽  
K. Koike ◽  
R. M. MacLeod
Keyword(s):  
Growth Hormone ◽  
Anterior Pituitary ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
Hormone Release ◽  
Growth Hormone Release ◽  
Concentration Dependent Manner ◽  
Anterior Pituitary Cells ◽  
Arachidonate Release

Arachidonate and its metabolites increase growth hormone release in vitro. A study was designed to determine whether arachidonate release from anterior pituitary cells is modified by growth hormone-releasing factor (GRF) or somatostatin (SRIF). Cultured pituitary cells were incubated with [3H]arachidonate to esterify the long-chain fatty acid into cellular lipids. The cells were extensively washed with medium containing no [3H]arachidonate and then incubated with GRF and/or SRIF for 30 min. The incubation medium was then extracted with ethyl acetate, and following thin-layer chromatographic separation, the radioactivity in the [3H]arachidonate band was measured. GRF in a concentration-dependent manner (1-30 nM) stimulated growth hormone and arachidonate release, whereas SRIF (100 nM) blocked the GRF-induced increase of growth hormone and arachidonate release. The effects of GRF on growth hormone and arachidonate were evident at time intervals as brief as 5 min. These findings support the hypothesis that arachidonate may play a role in the GRF-induced growth hormone release.

Maitotoxin increases inositol phosphates in rat anterior pituitary cells

1991 ◽  
Vol 6 (1) ◽  
pp. 95-99 ◽  
Author(s):  
M. A. Sortino ◽  
T. M. Delahunty ◽  
T. Yasumoto ◽  
M. J. Cronin
Keyword(s):  
Anterior Pituitary ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Cell Types ◽  
Calcium Stores ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Anterior Pituitary Cells ◽  
Intracellular Ca

ABSTRACT Maitotoxin is a potent marine poison that mobilizes calcium in most vertebrate cell types and accelerates secretion from anterior pituitary cells. It is not known whether voltage-sensitive calcium channels or other mechanisms initiate the effects of maitotoxin on anterior pituitary cells. Changes in intracellular Ca2+ levels may also be achieved by releasing internal calcium stores via inositol trisphosphate (InsP3). Indeed, maitotoxin rapidly increased inositol phosphate accumulation in a concentration-dependent manner. Calcium channel antagonists such as nifedipine and verapamil did not block this response nor did calcium-mobilizing agents (BAYk8644, A23187) mimic this effect. These data suggest that the mechanism by which maitotoxin acts at the pituitary may include the activation of an enzyme that produces the calcium-mobilizing signal InsP3.

Intracellular mechanisms involved in the stimulation of growth hormone release from rat anterior pituitary cells by Russell's viper venom

1990 ◽  
Vol 127 (1) ◽  
pp. 111-117 ◽  
Author(s):  
G. R. Hart ◽  
G. Caldwell ◽  
J. M. Burrin
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Anterior Pituitary ◽  
Pituitary Cells ◽  
Maximal Effect ◽  
Dependent Manner ◽  
Kinase C ◽  
Anterior Pituitary Cells ◽  
Russell’S Viper ◽  
Intracellular Mechanisms

ABSTRACT We have previously shown that a heat-stable component of Russell's viper venom (RVV) releases GH in a dose-dependent manner from cultured rat anterior pituitary cells. We have now investigated the intracellular mechanisms involved in RVV-stimulated GH release by concomitant administration of RVV with known intracellular mediators in rat pituitary cells. 3-Isobutyl-1-methylxanthine (IBMX; 0·5 mmol/l), added to cultured rat anterior pituitary cells simultaneously with RVV, at concentrations up to a maximally effective dose of 10 μg/ml, increased GH release (3·7-fold, 4·0-fold and 2·0-fold; P < 0·001) compared with the effect of venom alone. These effects were additive, indicating that RVV and IBMX stimulate through different intracellular messengers. RVV failed to increase the formation of basal or IBMX-stimulated intracellular cyclic AMP (cAMP), confirming that RVV affects GH release through a cAMP-independent pathway. 12-0-Tetradecanoylphorbol-13-acetate (TPA; 0·1 μmol/l), added simultaneously with various doses of RVV (0·1–10 μg/ml), did not increase GH release beyond the maximal effect of RVV. This result indicates that RVV might be stimulating GH release through a similar mechanism to that of TPA (by activating protein kinase C). When pituitary cells were perifused with Ca2+-free medium or verapamil (50 μmol/l), RVV-stimulated GH release was inhibited by 65 and 42% respectively. This reflects the recognized requirement of Ca2+ for secretory processes. However, RVV (10 μg/ml) had no significant effect on intracellular free Ca2+ concentrations as measured using the fluorescent Ca2+ probe quin-2. These findings indicate that the mechanism of action of RVV on GH release is independent of a change in both cAMP levels and intracellular free Ca2+ concentrations, and is dependent upon protein kinase C. Journal of Endocrinology (1990) 127, 111–117

Maitotoxin stimulates hormonal release and calcium flux in rat anterior pituitary cells in vitro

1984 ◽  
Vol 247 (4) ◽  
pp. E520-E525
Author(s):  
G. Schettini ◽  
K. Koike ◽  
I. S. Login ◽  
A. M. Judd ◽  
M. J. Cronin ◽  
...  
Keyword(s):  
Calcium Channels ◽  
Anterior Pituitary ◽  
Calcium Influx ◽  
Calcium Flux ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
Anterior Pituitary Cells ◽  
Lh Release ◽  
Hormonal Release

The marine dinoflagellate toxin maitotoxin (MTX), an activator of calcium channels, stimulates the release of prolactin (PRL), growth hormone (GH), thyroid-stimulating hormone (TSH), and luteinizing hormone (LH) from monolayers of anterior pituitary cells in a dose-dependent manner. Maitotoxin significantly increased PRL, GH, and LH release within 1.5 min and TSH release within 3.5 min, and the stimulation continued for at least 1 h (P less than 0.01). MTX-stimulated hormonal release was blocked by the calcium channel blocker manganese (P less than 0.01). In freshly dispersed perifused pituitary cells in columns, exposure to MTX for 10 min markedly increased PRL, GH, TSH, and LH release for at least 1 h after withdrawal of the toxin. In other experiments, MTX significantly stimulated 45Ca2+ exchange by dispersed pituitary cells within 30 s, continuing for at least 30 min. We conclude that MTX increases anterior pituitary hormonal release, possibly by activating calcium channels, thereby increasing cellular calcium influx. Thus MTX may be a useful agent for investigating the involvement of Ca2+ in hormonal secretory processes.

scholarly journals miR-361-3p regulates FSH by targeting FSHB in a porcine anterior pituitary cell model

Reproduction ◽  
2017 ◽  
Vol 153 (3) ◽  
pp. 341-349 ◽  
Author(s):  
Rui-Song Ye ◽  
Meng Li ◽  
Chao-Yun Li ◽  
Qi-En Qi ◽  
Ting Chen ◽  
...  
Keyword(s):  
Anterior Pituitary ◽  
Posttranscriptional Regulation ◽  
Cell Model ◽  
Human Reproduction ◽  
Luciferase Assay ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
Protein Levels ◽  
Anterior Pituitary Cells ◽  
Transcriptional Regulatory Mechanisms

FSH plays an essential role in processes involved in human reproduction, including spermatogenesis and the ovarian cycle. While the transcriptional regulatory mechanisms underlying its synthesis and secretion have been extensively studied, little is known about its posttranscriptional regulation. A bioinformatics analysis from our group indicated that a microRNA (miRNA; miR-361-3p) could regulate FSH secretion by potentially targeting the FSHB subunit. Herein, we sought to confirm these findings by investigating the miR-361-3p-mediated regulation of FSH production in primary pig anterior pituitary cells. Gonadotropin-releasing hormone (GnRH) treatment resulted in an increase in FSHB synthesis at both the mRNA, protein/hormone level, along with a significant decrease in miR-361-3p and its precursor (pre-miR-361) levels in time- and dose-dependent manner. Using the Dual-Luciferase Assay, we confirmed that miR-361-3p directly targets FSHB. Additionally, overexpression of miR-361-3p using mimics significantly decreased the FSHB production at both the mRNA and protein levels, with a reduction in both protein synthesis and secretion. Conversely, both synthesis and secretion were significantly increased following miR-361-3p blockade. To confirm that miR-361-3p targets FSHB, we designed FSH-targeted siRNAs, and co-transfected anterior pituitary cells with both the siRNA and miR-361-3p inhibitors. Our results indicated that the siRNA blocked the miR-361-3p inhibitor-mediated upregulation of FSH, while no significant effect on non-target expression. Taken together, our results demonstrate that miR-361-3p negatively regulates FSH synthesis and secretion by targeting FSHB, which provides more functional evidence that a miRNA is involved in the direct regulation of FSH.

scholarly journals Characterization of purinergic P2X4 receptor channels expressed in anterior pituitary cells

2010 ◽  
Vol 298 (3) ◽  
pp. E644-E651 ◽  
Author(s):  
Hana Zemkova ◽  
Marek Kucka ◽  
Shuo Li ◽  
Arturo E. Gonzalez-Iglesias ◽  
Melanija Tomic ◽  
...  
Keyword(s):  
Anterior Pituitary ◽  
Hormone Secretion ◽  
Maximum Amplitude ◽  
Thyrotropin Releasing Hormone ◽  
P2x Receptor ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
Specific Expression ◽  
Releasing Hormone ◽  
Anterior Pituitary Cells

Anterior pituitary cells express cation-conducting P2X receptor channels (P2XRs), but their molecular identity, electrophysiological properties, cell-specific expression pattern, and physiological roles have been only partially characterized. In this study, we show by quantitative RT-PCR that mRNA transcripts for the P2X4 subunit are the most abundant in rat anterior pituitary tissue and confirm the P2X4R protein expression by Western blot analysis. Single-cell patch-clamp recordings show that extracellular ATP induced an inward depolarizing current in a majority of thyrotropin-releasing hormone-responsive pituitary cells, which resembled the current profile generated by recombinant P2X4R. The channels were activated and desensitized in a dose-dependent manner and deactivated rapidly. Activation of these channels led to stimulation of electrical activity and promotion of voltage-gated and voltage-insensitive Ca2+ influx. In the presence of ivermectin, a specific allosteric modulator of P2X4Rs, there was an approximately fourfold increase in the maximum amplitude of the ATP-induced inward current, accompanied by an increase in the sensitivity of receptors for ATP, slowed deactivation of receptors, and enhanced ATP-induced prolactin release. These results indicate that thyrotropin-releasing hormone-responsive cells, including lactotrophs, express homomeric and/or heteromeric P2X4Rs, which facilitate Ca2+ influx and hormone secretion.

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