scholarly journals Inhibitory effects of antagonistic analogs of GHRH on GH3 pituitary cells overexpressing the human GHRH receptor

2002 ◽  
Vol 175 (2) ◽  
pp. 425-434 ◽  
Author(s):  
M Kovacs ◽  
AV Schally ◽  
EJ Lee ◽  
R Busto ◽  
P Armatis ◽  
...  
Keyword(s):  
Gh3 Cells ◽  
Intracellular Camp ◽  
Pituitary Cells ◽  
Gh Secretion ◽  
Ghrh Receptor ◽  
Infected Cells ◽  
Ghrh Antagonists ◽  
Rat Pituitary Tumor Cells ◽  
Potent Antagonist ◽  
Dose Dependent

GH3 rat pituitary tumor cells produce GH and prolactin (PRL), but lack the GHRH receptor (GHRH-R). We expressed human GHRH-R (hGHRH-R) in GH3 cells using recombinant adenoviral vectors and studied the effects of GHRH antagonists. The mRNA expression of the GHRH-R gene in the cells was demonstrated by RT-PCR. An exposure of the GH3 cells infected with hGHRH-R to 10(-10), 10(-9) and 10(-8) m hGHRH for 1 or 2 h in culture caused a dose-dependent elevation of the intracellular cAMP concentration and the cAMP efflux. Exposure to hGHRH also elicited dose-dependent increases in GH and PRL secretion from these cells. Neither the uninfected nor the antisense hGHRH-R-infected control cells exhibited cAMP, GH and PRL responses to GHRH stimulation. GHRH antagonists JV-1-38 and jv-1-36 applied at 3x10(-8) m for 3 h, together with 10(-9) m GHRH, significantly inhibited the GHRH-stimulated cAMP efflux from the hGHRH-R-infected cells by 36 and 80% respectively. The more potent antagonist JV-1-36 also decreased the intracellular cAMP levels in these cells by 55%. Exposure to JV-1-36 for 1 h nullified the stimulatory effect of GHRH on GH secretion and significantly inhibited it by 64 and 77% after 2 and 3 h respectively. In a superfusion system, GHRH at 10(-10), 10(-9) and 10(-8) m concentrations induced prompt and dose-related high cAMP responses and smaller increases in the spontaneous GH secretion of the hGHRH-R-infected cells. Antagonists JV-1-36 and JV-1-38 applied at 3x10(-8) m for 15 min, together with 10(-9) m GHRH, inhibited the GHRH-stimulated cAMP response by 59 and 35% respectively. This work demonstrates that GHRH antagonists can effectively inhibit the actions of GHRH on the hGHRH-R. Our results support the view that this class of compounds would be active clinically.

scholarly journals Mechanism of liver-selective thyromimetic activity of SK&F L-94901: evidence for the presence of a cell-type-specific nuclear iodothyronine transport process

2000 ◽  
Vol 165 (2) ◽  
pp. 391-397 ◽  
Author(s):  
K Ichikawa ◽  
T Miyamoto ◽  
T Kakizawa ◽  
S Suzuki ◽  
A Kaneko ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Transport Process ◽  
Hormone Receptors ◽  
Gh3 Cells ◽  
Pituitary Cells ◽  
Intact Cells ◽  
Hepatic Cells ◽  
Rat Pituitary Tumor Cells ◽  
Responsive Element ◽  
Hormone Responsive Element

The thyromimetic compound SK&F L-94901 shows more potent thyromimetic activity in the liver than in the pituitary gland or heart when administered to rats. The mechanisms of liver-selectivity of SK&F L-94901 were examined using cultured rat hepatoma cells (dRLH-84) and rat pituitary tumor cells (GH3), both of which showed saturable cellular uptake of tri-iodothyronine (T(3)). When isolated nuclei with partial disruption of the outer nuclear membrane were used, SK L-94901 competed for [(125)I]T(3) binding to nuclear receptors almost equally in dRLH-84 and GH3 cells. SK L-94901 also did not discriminate thyroid hormone receptors (TR) alpha1 and beta1 in terms of binding affinity and activation of the thyroid hormone responsive element. In intact cells, however, SK L-94901 was a more potent inhibitor of nuclear [(125)I]T(3) binding in dRLH-84 cells than in GH3 cells at an early phase of the nuclear uptake process and after binding equilibrium. These data suggest that SK L-94901 is more effectively transported to nuclear TRs in hepatic cells than in pituitary cells and therefore shows liver-selective thyromimetic activity. In conclusion, SK L-94901 discriminates hepatic cells and pituitary cells at the nuclear transport process. The cellular transporters responsible for this discrimination were not evident.

scholarly journals Is GHRH Receptor Essential to GHRP-2-Induced GH Secretion in Primary Cultured Rat Pituitary Cells?

Endocrinology ◽  
2002 ◽  
Vol 143 (5) ◽  
pp. 1964-1967 ◽  
Author(s):  
Sang-Gun Roh ◽  
Chen Chen ◽  
Ki-Choon Choi ◽  
Yogendra Shrestha ◽  
Shin-Ichi Sasaki
Keyword(s):  
Pituitary Cells ◽  
Gh Secretion ◽  
Ghrh Receptor ◽  
Rat Pituitary ◽  
Rat Pituitary Cells

Synergistic interaction in bovine pituitary cultures between growth hormone-releasing factor and other hypophysiotrophic factors

1986 ◽  
Vol 109 (1) ◽  
pp. 67-74 ◽  
Author(s):  
C. D. Ingram ◽  
R. J. Bicknell
Keyword(s):  
Growth Hormone ◽  
Synergistic Interaction ◽  
Pituitary Cells ◽  
Prolactin Release ◽  
Thyrotrophin Releasing Hormone ◽  
Growth Hormone Releasing Factor ◽  
Gh Secretion ◽  
Similar Dose ◽  
Effective Doses ◽  
Dose Dependent

ABSTRACT Synthetic human pancreatic GH-releasing factor (1–44)NH2 (GRF) and acetylcholine (ACh) were shown to evoke a dose-related release of GH from cultured bovine pituitary cells with half-maximal effective doses of 0·3 and 500 nmol/l respectively. Concentrations of ACh (10 μmol/l) and GRF (25 nmol/l) which were shown to give near maximal responses when presented alone, produced highly synergistic responses when tested in combination. This synergism was related to the ACh concentration employed, and both the ACh-induced release and ACh-induced synergism were abolished by the muscarinic antagonist, atropine. A synergistic interaction was also demonstrated between GRF and concentrations of thyrotrophin-releasing hormone (TRH) and bombesin which, in the absence of GRF, failed to elicit significant GH release. Acetylcholine stimulated a similar dose-dependent release of prolactin, but GRF was ineffectual in either directly stimulating prolactin release or affecting the response to ACh or TRH. No synergistic interaction could be detected between combinations of ACh and TRH or between ACh and bombesin. The data suggest that, in the somatotroph, GRF acts through a different second messenger pathway to ACh, TRH and bombesin and that these two pathways can be activated to produce a potentiated response. Growth hormone-releasing factor is, therefore, not only a specific GH secretagogue, but may act in concert with other hypophysiotrophic factors to regulate GH secretion from the bovine anterior pituitary. J. Endocr. (1986) 109, 67–74

scholarly journals Effect of activin on production and secretion of prolactin and growth hormone in cultured rat GH3 cells

2000 ◽  
pp. 506-511 ◽  
Author(s):  
N Tamura ◽  
M Irahara ◽  
A Kuwahara ◽  
K Ushigoe ◽  
H Sugino ◽  
...  
Keyword(s):  
Gene Expression ◽  
Activin A ◽  
Gh3 Cells ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Inhibitory Effects ◽  
Gh Secretion ◽  
Gh Gene ◽  
Dose Dependent ◽  
Cells Cultured

OBJECTIVE: To evaluate the effect of the growth factor activin A on the secretion of prolactin (PRL) and GH in cultured GH3 cells. METHODS: The concentrations of PRL and GH secreted from GH3 cells cultured in media with and without activin A were measured by RIA, and the expression of PRL mRNA and GH mRNA were analyzed using the Northern blot method. RESULTS: Activin A significantly inhibited PRL release from GH3 cells cultured for 48h in a dose-dependent manner (activin: 0.3-3nM). The inhibitory effects of 3nM activin A were observed in the culture from 12h to 48h (53.2% of control). Activin A (3nM) also significantly inhibited the expression of PRL mRNA at 24h (33.8% of control). In contrast, activin A significantly stimulated GH release from GH3 cells cultured for 48h in a dose-dependent manner (activin: 0.3-3nM). The stimulatory effect of 3nM activin A was observed in the culture for 48h (157.6% of control). Activin A (3nM) also significantly stimulated the expression of GH mRNA at 24h (183.6% of control). In spite of these significant changes in PRL and GH secretion, pit-1 mRNA levels were not significantly changed by activin A. CONCLUSIONS: These findings indicated that activin A modulates PRL and GH secretion through the regulation of PRL and GH gene transcription in GH3 cells, but that these effects are unrelated to pit-1 gene expression.

scholarly journals Ghrelin-induced GH secretion in domestic fowl in vivo and in vitro

2003 ◽  
Vol 179 (1) ◽  
pp. 97-105 ◽  
Author(s):  
ML Baudet ◽  
S Harvey
Keyword(s):  
Domestic Fowl ◽  
Mammalian Species ◽  
Plaque Assay ◽  
Pituitary Cells ◽  
Direct Effects ◽  
Gh Secretion ◽  
Dose Dependent Increase ◽  
Dose Dependent

Although avian and mammalian species differ significantly in their regulation of GH secretion, preliminary studies have demonstrated in vivo GH responses to ghrelin in chickens, as in mammals. However, the relative potency of ghrelin as a GH-releasing hormone (GHRH) in birds is uncertain, as is its site of action.The intravenous administration of human ghrelin to immature chickens promptly increased the circulating GH concentration (within 10 min), although this was transitory and was only maintained for 20 min. This GH response was dose-related with an EC50 of approximately 3.0 microg/kg, comparable with the reported potency of human GHRH in chickens. When incubated with dispersed pituitary cells, human ghrelin induced dose-dependent GH release over a range of 10(-6) to 10(-9) M, with an EC50 of 7.0 x 10(-8) M, comparable with that induced by human GHRH (EC50 6.0 x 10(-8) M), although it was less effective at doses of 10(-6) to 10(-8) M. This was due to direct effects on pituitary somatotrophs, since human ghrelin increased GH release (determined by the reverse hemolytic plaque assay) from individual pituitary cells. The incubation of these cells with human ghrelin induced a dose-dependent increase in the numbers of somatotrophs secreting GH and in the amount of GH released by each cell. In summary, these results demonstrated that ghrelin is a dose-related GH-releasing factor in chickens with a potency comparable with that induced by human GHRH. The GH-releasing action of ghrelin is due, at least in part, to stimulatory actions on the numbers of somatotrophs induced to release GH and upon the amount of GH released from individual somatotrophs.

scholarly journals Antagonists of Growth Hormone-Releasing Hormone Inhibit the Growth of Pituitary Adenoma Cells by Hampering Oncogenic Pathways and Promoting Apoptotic Signaling

Cancers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 3950
Author(s):  
Iacopo Gesmundo ◽  
Giuseppina Granato ◽  
Antonio C. Fuentes-Fayos ◽  
Clara V. Alvarez ◽  
Carlos Dieguez ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Cell Viability ◽  
Cancer Progression ◽  
Intracellular Camp ◽  
Growth Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Ghrh Receptor ◽  
Ghrh Antagonists

Pituitary adenomas (PAs) are intracranial tumors, often associated with excessive hormonal secretion and severe comorbidities. Some patients are resistant to medical therapies; therefore, novel treatment options are needed. Antagonists of growth hormone-releasing hormone (GHRH) exert potent anticancer effects, and early GHRH antagonists were found to inhibit GHRH-induced secretion of pituitary GH in vitro and in vivo. However, the antitumor role of GHRH antagonists in PAs is largely unknown. Here, we show that the GHRH antagonists of MIAMI class, MIA-602 and MIA-690, inhibited cell viability and growth and promoted apoptosis in GH/prolactin-secreting GH3 PA cells transfected with human GHRH receptor (GH3-GHRHR), and in adrenocorticotropic hormone ACTH-secreting AtT20 PA cells. GHRH antagonists also reduced the expression of proteins involved in tumorigenesis and cancer progression, upregulated proapoptotic molecules, and lowered GHRH receptor levels. The combination of MIA-690 with temozolomide synergistically blunted the viability of GH3-GHRHR and AtT20 cells. Moreover, MIA-690 reduced both basal and GHRH-induced secretion of GH and intracellular cAMP levels. Finally, GHRH antagonists inhibited cell viability in human primary GH- and ACTH-PA cell cultures. Overall, our results suggest that GHRH antagonists, either alone or in combination with pharmacological treatments, may be considered for further development as therapy for PAs.

scholarly journals GHRH excess and blockade in X-LAG syndrome

2015 ◽  
Vol 23 (3) ◽  
pp. 161-170 ◽  
Author(s):  
Adrian F Daly ◽  
Philippe A Lysy ◽  
Céline Desfilles ◽  
Liliya Rostomyan ◽  
Amira Mohamed ◽  
...  
Keyword(s):  
Receptor Antagonist ◽  
Young Female ◽  
Prolactin Secretion ◽  
Pituitary Cells ◽  
Therapeutic Blockade ◽  
Ghrelin Receptor ◽  
Gh Secretion ◽  
Ghrh Receptor ◽  
Ghrelin Receptor Agonist

X-linked acrogigantism (X-LAG) syndrome is a newly described form of inheritable pituitary gigantism that begins in early childhood and is usually associated with markedly elevated GH and prolactin secretion by mixed pituitary adenomas/hyperplasia. Microduplications on chromosome Xq26.3 including the GPR101 gene cause X-LAG syndrome. In individual cases random GHRH levels have been elevated. We performed a series of hormonal profiles in a young female sporadic X-LAG syndrome patient and subsequently undertook in vitro studies of primary pituitary tumor culture following neurosurgical resection. The patient demonstrated consistently elevated circulating GHRH levels throughout preoperative testing, which was accompanied by marked GH and prolactin hypersecretion; GH demonstrated a paradoxical increase following TRH administration. In vitro, the pituitary cells showed baseline GH and prolactin release that was further stimulated by GHRH administration. Co-incubation with GHRH and the GHRH receptor antagonist, acetyl-(d-Arg2)-GHRH (1-29) amide, blocked the GHRH-induced GH stimulation; the GHRH receptor antagonist alone significantly reduced GH release. Pasireotide, but not octreotide, inhibited GH secretion. A ghrelin receptor agonist and an inverse agonist led to modest, statistically significant increases and decreases in GH secretion, respectively. GHRH hypersecretion can accompany the pituitary abnormalities seen in X-LAG syndrome. These data suggest that the pathology of X-LAG syndrome may include hypothalamic dysregulation of GHRH secretion, which is in keeping with localization of GPR101 in the hypothalamus. Therapeutic blockade of GHRH secretion could represent a way to target the marked hormonal hypersecretion and overgrowth that characterizes X-LAG syndrome.

The effects of GH-releasing peptide-6 (GHRP-6) and GHRP-2 on intracellular adenosine 3′,5′-monophosphate (cAMP) levels and GH secretion in ovine and rat somatotrophs

1996 ◽  
Vol 148 (2) ◽  
pp. 197-205 ◽  
Author(s):  
D Wu ◽  
C Chen ◽  
J Zhang ◽  
C Y Bowers ◽  
I J Clarke
Keyword(s):  
Additive Effect ◽  
Intracellular Camp ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
Camp Accumulation ◽  
Gh Secretion ◽  
Rat Pituitary ◽  
Rat Pituitary Cells ◽  
Camp Levels

Abstract The mechanism of action of GH-releasing peptide-6 (GHRP-6) and GHRP-2 on GH release was investigated in ovine and rat pituitary cells in vitro. In partially purified sheep somatotrophs, GHRP-2 and GH-releasing factor (GRF) increased intracellular cyclic AMP (cAMP) concentrations and caused GH release in a dose-dependent manner; GHRP-6 did not increase cAMP levels. An additive effect of maximal doses of GRF and GHRP-2 was observed in both cAMP and GH levels whereas combined GHRP-6 and GHRP-2 at maximal doses produced an additive effect on GH release only. Pretreatment of the cells with MDL 12,330A, an adenylyl cyclase inhibitor, prevented cAMP accumulation and the subsequent release of GH that was caused by either GHRP-2 or GRF. The cAMP antagonist, Rp-cAMP also blocked GH release in response to GHRP-2 and GRF. The cAMP antagonist did not prevent the effect of GHRP-6 on GH secretion whereas MDL 12,330A partially reduced the effect. An antagonist for the GRF receptor, [Ac-Tyr1,d-Arg2]-GRF 1–29, significantly diminished the effect of GHRP-2 and GRF on cAMP accumulation and GH release, but did not affect GH release induced by GHRP-6. Somatostatin prevented cAMP accumulation and GH release responses to GHRP-2, GRF and GHRP-6. Ca2+ channel blockade did not affect the cAMP increase in response to GHRP-2 or GRF but totally prevented GH release in response to GHRP-2, GRF and GHRP-6. These results indicated that GHRP-2 acts on ovine pituitary somatotrophs to increase cAMP concentration in a manner similar to that of GRF; this occurs even during the blockade of Ca2+ influx. GHRP-6 caused GH release without an increase in intracellular cAMP levels. GH release in response to all three secretagogues was reduced by somatostatin and was dependent upon the influx of extracellular Ca2+. The additive effect of GHRP-2 and GRF or GHRP-6 suggested that the three peptides may act on different receptors. In rat pituitary cell cultures, GHRP-6 had no effect on cAMP levels, but potentiated the effect of GRF on cAMP accumulation. The synergistic effect of GRF and GHRP-6 on cAMP accumulation did not occur in sheep somatotrophs. Whereas GHRP-2 caused cAMP accumulation in sheep somatotrophs, it did not do so in rat pituitary cells. These data indicate species differences in the response of pituitary somatotrophs to the GHRPs and this is probably due to different subtypes of GHRP receptor in rat or sheep. Journal of Endocrinology (1996) 148, 197–205

Interaction of dihydropyridine Ca2+ agonist Bay K 8644 with normal and transformed pituitary cells

1986 ◽  
Vol 250 (1) ◽  
pp. C95-C102 ◽  
Author(s):  
J. J. Enyeart ◽  
T. Aizawa ◽  
P. M. Hinkle
Keyword(s):  
Neuronal Cell ◽  
Bay K 8644 ◽  
Pituitary Cells ◽  
Neuronal Cell Bodies ◽  
Rat Pituitary ◽  
Normal Rat ◽  
Rat Pituitary Tumor Cells ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Ca2 Channels

The dihydropyridine (DHP) Ca2+ agonist Bay K 8644 produced a dose-dependent increase in 45Ca2+ uptake by GH4C1 rat pituitary tumor cells. For agonist concentrations between 10(-9) and 10(-5) M, the enhanced 45Ca2+ uptake was well correlated with simultaneous increases in prolactin (PRL) secretion. Bay K 8644 combined with depolarizing concentrations of KCl produced more than additive effects on net Ca2+ uptake and hormone release. Nisoldipine, a DHP Ca2+ antagonist, competitively blocked Bay K 8644-stimulated 45Ca2+ uptake. This drug also potently inhibited 45Ca2+ uptake triggered by depolarization with KCl (estimated half-maximal inhibiting concentration: 2 nM). Bay K 8644 enhanced PRL secretion from normal rat pituitaries in culture and in a perifusion system. These results indicate that Bay K 8644 is a potent modulator of voltage-sensitive Ca2+ channels of both normal and transformed pituitary cells. In this respect endocrine cell Ca2+ channels resemble those found in heart, smooth muscle, and neuronal cell bodies.

Inhibition of L-692,429-stimulated rat growth hormone release by a weak substance P antagonist: L-756,867

1997 ◽  
Vol 152 (1) ◽  
pp. 155-158 ◽  
Author(s):  
K Cheng ◽  
L Wei ◽  
L-Y Chaung ◽  
W W-S Chan ◽  
B Butler ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Substance P ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
Gh Secretion ◽  
Substance P Antagonist ◽  
The Right ◽  
Dose Dependent

Abstract H2N,d-Arg,Pro,Lys,Pro,d-Phe,Gln,d-Trp,Phe,d-Trp,Leu, Leu,NH2 (L-756,867), a weak substance P antagonist, inhibited L-692,429-stimulated GH release from rat primary pituitary cells in a dose-dependent manner. At a concentration of 50 nm, L-756,867 shifted the dose–response curve of L-692,429-induced GH release to the right by about tenfold. It also impaired the ability of L-692,429 to potentiate the effect of growth hormone-releasing factor (GRF) on GH release. Substance P (1 μm) had no effect on basal or L-692,429-stimulated GH release. When tested in anesthetized rats, L-756,867 inhibited L-692,429- and growth hormone-releasing hexapeptide- (GHRP-6)-stimulated GH secretion in a dose-dependent manner. Complete inhibition was observed at an i.v. dose of 100 μg/kg of L-756,867. However, at the same concentration, it had no effect on GRF-induced GH secretion. d-Lys3-GHRP-6, a GHRP-6 antagonist, had no effect on GHRP-6 or L-692,429-induced GH secretion even at an i.v. dose of 2 mg/kg. These results indicate that L-692,429 and GHRP-6 stimulate GH release both in vitro and in vivo via a common receptor and signaling pathway which is different from that of substance P in spite of the fact that their effects are inhibited by a weak substance P antagonist. Journal of Endocrinology (1997) 152, 155–158

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