Growth Hormone Cells Research Articles

Abstract A185: Menin functions as a gatekeeper of the proliferative MAPK arm of K-Ras signaling.

Abstract Activating mutations of the prototypical oncogene KRAS drive proliferation in all pancreatic ductal adenocarcimomas, but have never been found in pancreatic endocrine tumors, which more commonly inactivate tumor suppressors such as MEN1, the gene mutated in the autosomal dominant cancer syndrome Multiple Endocrine Neoplasia type 1, showing that outcomes of K-Ras signaling depend on cellular context. We have shown that K-Ras does not promote but instead strongly suppresses endocrine cell growth and that this paradoxical activity derives from the Men1 gene product Menin. We have proposed a model in which K-Ras activates both the pro-proliferative MAPK pathway, and the anti-proliferative RASSF1 pathway. In tissues susceptible to MEN1 gene mutation, Menin normally prevents the MAPK effector pathway from driving proliferation while leaving the inhibitory RASSF1 effector pathway intact. In this model, loss of Menin causes proliferation due to removal of the block in MAPK-driven proliferation downstream of K-Ras, while loss of K-Ras signaling increases proliferation by decreasing the unopposed RASSF1 activity in susceptible cells. To test this model, we assessed the effect of various inhibitors of the K-Ras pathway on beta cell proliferation in cultured mouse islets. We found that treatment with a combination of farnesyl- and geranyl-geranyl-transferase inhibitors, which block K-Ras signaling, stimulated beta cell proliferation; but blocking MAPK signaling with an inhibitor of Mek1/2 had no effect on proliferation rate. However, in beta-cells with reduced Men1 gene dosage, both K-Ras and Mek1/2 inhibition reduced the increased basal replication rate, consistent with our model that Menin specifically blocks pro-proliferative outputs of the MAPK arm of K-Ras signaling. Remarkably, complete loss of Men1 created a synthetic lethal interaction with Mek1/2 inhibition. Our study suggests that inhibitors of the Raf/MEK/ERK pathway offer a rational therapy for tumors with germline or somatic MEN1 mutations. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A185. Citation Format: Chester Chamberlain, Michael German. Menin functions as a gatekeeper of the proliferative MAPK arm of K-Ras signaling. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A185.

Immunohistochemical study of pituitary cells in wild and captive Salminus hilarii (Characiformes: Characidae) females during the annual reproductive cycle

Freshwater fish that live exclusively in rivers are at particular risk from fragmentation of the aquatic system, mainly the species that migrate upriver for reproduction. That is the case of Salminus hilarii, an important migratory species currently classified as “almost threatened” in the São Paulo State (Brazil), facing water pollution, dam construction, riparian habitat destruction and environmental changes that are even more serious in this State. Additionally, this species show ovulation dysfunction in captivity. Our studies focused on the identification and distribution of the pituitary cell types in the adenohypophysis of S. hilarii females, including a morphometric analysis that compares pituitary cells from wild and captive broodstocks during the reproductive annual cycle. The morphology of adenohypophysial cells showed differences following the reproductive cycle and the environment. In general, optical density suggested a higher cellular activity during the previtellogenic (growth hormone) and vitellogenic (somatolactin) stages in both environments. Additionally, the nucleus/cell ratio analysis suggested that growth hormone and somatolactin cells were larger in wild than in captive females in most reproductive stages of the annual cycle. In contrast, prolactin hormone showed no variation throughout the reproductive cycle (in both environments). Morphometrical analyses related to reproduction of S. hilarii in different environmental conditions, suggest that somatolactin and growth hormone play an important role in reproduction in teleost and can be responsible for the regulation of associated processes that indirectly affect reproductive status.

Late Primary Autoimmune Hypothyroidism in a Patient with Postdelivery Autoimmune Hypopituitarism Associated with Antibodies to Growth Hormone and Prolactin-Secreting Cells

Pituitary and thyroid autoimmunity can be triggered by pregnancy. We report the first association of combined growth hormone (GH) and prolactin secretion deficiency due to autoimmune damage to GH- and prolactin-secreting cells in a patient with postdelivery lactation failure, presenting subsequently with primary autoimmune hypothyroidism. A 34-year-old woman presented with lactation failure following the delivery of her first child. She had a family history of hypothyroidism without a history of pituitary dysfunction. Physical examination did not show any abnormal findings. Laboratory investigations showed normal gonadotropin levels after the restoration of normal menstrual cycles following pregnancy, normal basal and stimulated cortisol levels, but an impaired GH response to insulin-induced hypoglycemia, and low basal prolactin and insulin-like growth factor-1 concentrations. Thyroid function was normal when initially investigated three months after delivery, but five months later, marked primary hypothyroidism (thyrotropin levels >100 mIU/L) occurred. Immunological investigation revealed the presence of antipituitary antibodies, identified by double immunofluorescence and targeting GH- and prolactin-secreting cells. Antithyroid antibodies, in the normal range three months postpartum, became significantly elevated when the hypothyroidism appeared. Autoimmune hypophysitis is responsible for selective or multiple pituitary-hormone deficiencies, sometimes involving thyrotropin secretion and causing secondary hypothyroidism, but usually associated with hyperprolactinemia. To our knowledge, this is the first observation of autoimmune hypopituitarism involving deficient growth hormone and prolactin secretion in a patient with lactation failure after delivery, subsequently followed by severe primary autoimmune hypothyroidism, thus falling into an unusual constellation of autoimmune polyendocrine syndrome type 3. Considering the well-known relationship between pregnancy and autoimmunity, an early postdelivery immunological and functional investigation in women presenting with disorders of lactation may be useful to detect potential pituitary and thyroid dysfunction even at a subclinical stage.

Pituitary Phenotypes of Mice Lacking the Notch Signalling Ligand Delta‐Like 1 Homologue

The Notch signalling pathway ligand delta-like 1 homologue (Dlk1, also named Pref1) is expressed throughout the developing pituitary and becomes restricted to mostly growth hormone (GH) cells within the adult gland. We have investigated the role of Dlk1 in pituitary development and function from late embryogenesis to adulthood using a mouse model completely lacking the expression of Dlk1. We confirm that Dlk1-null mice are shorter and weigh less than wild-type littermates from late gestation, at parturition and in adulthood. A loss of Dlk1 leads to significant reduction in GH content throughout life, whereas other pituitary hormones are reduced to varying degrees depending on sex and age. Both the size of the pituitary and the proportion of hormone-producing cell populations are unchanged, suggesting that there is a reduction in hormone content per cell. In vivo challenge of mutant and wild-type littermates with growth hormone-releasing hormone and growth hormone-releasing hexapeptide shows that reduced GH secretion is unlikely to account for the reduced growth of Dlk1 knockout animals. These data suggest that loss of Dlk1 gives rise to minor pituitary defects manifesting as an age- and sex-dependent reduction in pituitary hormone contents. However, Dlk1 expression in other tissue is most likely responsible for the weight and length differences observed in mutant animals.

Anterior pituitary cell networks.

Both endocrine and non-endocrine cells of the pituitary gland are organized into structural and functional networks which are formed during embryonic development but which may be modified throughout life. Structural mapping of the various endocrine cell types has highlighted the existence of distinct network motifs and relationships with the vasculature which may relate to temporal differences in their output. Functional characterization of the network activity of growth hormone and prolactin cells has revealed a role for cell organization in gene regulation, the plasticity of pituitary hormone output and remarkably the ability to memorize altered demand. As such, the description of these endocrine cell networks alters the concept of the pituitary from a gland which simply responds to external regulation to that of an oscillator which may memorize information and constantly adapt its coordinated networks' responses to the flow of hypothalamic inputs.

Role of thymulin on the somatotropic axis in vivo

AimsThere is clear evidence for the existence of a bi-directional thymus–somatotropic axis and several studies suggest that the thymic peptide thymulin may be involved in this communication. We undertook to assess the impact of serum thymulin immunoneutralization in C57BL/6 mice and that of neonatal thymulin gene therapy (NTGT) in nude mice on body weight (BW) gain and on the histomorphometric profile of the somatotrope population. Main methodsImmunoneutralization of thymulin was done from postnatal day 1 to 35 by i.p. injections of rabbit anti-thymulin serum (α-FTS) and normal rabbit serum (NRS) in controls. NTGT was implemented in nudes using an adenoviral vector expressing a synthetic gene for thymulin (RAd-FTS). On postnatal day 1, heterozygous (nu/+) and homozygous (nu/nu) pups received a single bilateral i.m. injection either RAd-FTS or RAd-GFP (a control vector expressing green fluorescent protein). BW gain was recorded and at the end of the study the pituitaries were immunostained for growth hormone (GH). Serum GH and thymulin were determined by radioimmunoassay and bioassay, respectively. Key findingsThymulin immunoneutralization induced a significant decrease in BW gain, serum GH and somatotrope cell density as well as an increase in somatotrope cell size. NTGT markedly increased BW gain, serum thymulin (P<0.01) and somatotrope cell and volume density in nu/nu mice. SignificanceOur results suggest that thymulin plays a relevant physiological role on the thymus–somatotropic axis in mice.

Transdifferentiation of pituitary thyrotrophs to lactothyrotrophs in primary hypothyroidism: case report

Primary hypothyroidism causes adenohypophysial hyperplasia via stimulation by hypothalamic thyrotropin-releasing hormone (TRH). The effect was long thought to simply result in thyroid-stimulating hormone (TSH) and prolactin (PRL) cell hyperplasia, an increase in TSH and PRL blood levels with resultant pituitary enlargement, often mimicking adenoma. Recently, it was shown that transformation of growth hormone (GH) cells into TSH cells takes place in both clinical and experimental primary hypothyroidism. Such shifts from one cell to another with a concomitant change in hormone production are termed "transdifferentiation" and involve the gradual acquisition of morphologic features of thyrotrophs ("somatothyrotrophs"). We recently encountered a unique case of pituitary hyperplasia in a 40-year-old female with primary hypothyroidism wherein increased TSH production was by way of PRL cell recruitment. The resultant "lactothyrotrophs" maintained TSH cell morphology (cellular elongation and prominence of PAS-positive lysosomes) but expressed immunoreactivity for both hormones. No co-expression of GH was noted nor was thyroidectomy cells seen. This form of transdifferentiation has not previously been described.

Label-free differentiation of human pituitary adenomas by FT-IR spectroscopic imaging

Fourier transform infrared (FT-IR) spectroscopic imaging has been used to characterize different types of pituitary gland tumors and normal pituitary tissue. Freshly resected tumor tissue from surgery was prepared as thin cryosections and examined by FT-IR spectroscopic imaging. Tissue types were discriminated via k-means cluster analysis and a supervised classification algorithm based on linear discriminant analysis. Spectral classification allowed us to discriminate between tumor and non-tumor cells, as well as between tumor cells that produce human growth hormone (hGH+) and tumor cells that do not produce that hormone (hGH-). The spectral classification was compared and contrasted with a histological PAS and orange G stained image. It was further shown that hGH+ pituitary tumor cells show stronger amide bands than tumor cells that do not produce hGH. This study demonstrates that FT-IR spectroscopic imaging can not only potentially serve as a fast and objective approach for discriminating pituitary gland tumors from normal tissue, but that it can also detect hGH-producing tumor cells.

A tridimensional view of pituitary development and function

Recent advances in tridimensional (3D) tissue imaging have considerably enriched our view of the pituitary gland and its development. Whereas traditional histology of the pituitary anterior lobe portrayed this tissue as a patchwork of cells, 3D imaging revealed that cells of each lineage form extensive and structured homotypic networks. In the adult gland these networks contribute to the robustness and coordination of the cell response to secretagogs. In addition, the network organization adapts to changes in endocrine environment, as revealed by the sexually dimorphic growth hormone (GH) cell network. Further work is required to establish better the molecular basis for homotypic and heterotypic interactions in the pituitary as well as the implications of these interactions for pituitary function and dysfunction in humans.

Epidermal Growth Factor‐Activated Extracellular Signal‐Regulated Kinase Suppresses Growth Hormone Expression and Stimulates Proliferation in MtT/ E Cells

The mechanism for the inhibition of growth hormone (GH) expression by the epidermal growth factor (EGF) was examined in two clonal cell lines, MtT/E and MtT/S. The former has a negligible basal level of GH, whereas the latter has a high basal GH. The treatment of MtT/E cells with retinoic acid resulted in a significant increase in GH mRNA and subsequently GH. This stimulatory response to retinoic acid was strongly suppressed by EGF. This suppression was associated with an increase in the phosphorylation of extracellular signal-regulated kinase 1 and 2 (Erk1/2). The MEK [mitogen-activated protein kinase (MAPK) kinases that activate ERK1 and ERK2] inhibitor, PD98059, clearly inhibited the phosphorylation of Erk1/2 and restored the stimulatory effects of retinoic acid. These results suggest that the inhibitory effects of EGF on GH expression are mediated by MAPK activation in these cells. By contrast to the GH-producing clones examined previously, EGF showed a marked stimulation of proliferation of the MtT/E cells through a mechanism dependent on MAPK activation. On the other hand, the inhibitory effect of EGF on GH expression was less pronounced and the stimulation of cellular proliferation was not seen in MtT/S cells, even though it induced Erk-phosphorylation similar to that seen in MtT/E. The distinct difference in the response to EGF between these two GH cell lines appears to be attributed to differences in the function of MAPK cascade in each cell line. This may reflect the developmental stage of the cells from which MtT/E and MtT/S are derived.

Melanin concentrating hormone (MCH) is involved in the regulation of growth hormone in Cichlasoma dimerus (Cichlidae, Teleostei)

Growth hormone (GH) is the main pituitary hormone involved in somatic growth. In fish, the neuroendocrine control of GH is multifactorial due to the interaction of multiple inhibitors and stimulators. Melanin-concentrating hormone (MCH) is a cyclic peptide involved in skin color regulation of fish. In addition, MCH has been related to the regulation of food intake in both mammals and fish. There is only one report presenting evidences on the GH release stimulation by MCH in mammals in experiments in vitro, but there are no data on non-mammals. In the present work, we report for the first time the sequence of MCH and GH cDNA in Cichlasoma dimerus, a freshwater South American cichlid fish. We detected contacts between MCH fibers and GH cells in the proximal pars distalis region of the pituitary gland by double label confocal immunofluorescence indicating a possible functional relationship. Besides, we found that MCH increased GH transcript levels and stimulated GH release in pituitary cultures. Additionally, C. dimerus exposed to a white background had a greater number of MCH neurons with a larger nuclear area and higher levels of MCH transcript than those fish exposed to a black background. Furthermore, fish reared for 3months in a white background showed a greater body weight and total length compared to those from black background suggesting that MCH might be related to somatic growth in C. dimerus. Our results report for the first time, that MCH is involved in the regulation of the synthesis and release of GH in vitro in C. dimerus, and probably in the fish growth rate.

Immunocytochemical identification and distribution of the cell types in the pituitary gland of &amp;lt;i&amp;gt;Bagrus bayad&amp;lt;/i&amp;gt; (&amp;lt;i&amp;gt;Teleostei, Bagridae&amp;lt;/i&amp;gt;)

Immunocytochemical identification of the different cell types in the pituitary gland of Bagrus bayad was performed using antisera against mammalian (human and rat) and piscine hormones. The adenohypophysis was composed of rostral pars distalis (RPD), proximal pars distalis (PPD) and pars intermedia (PI). Prolactin and adrenocorticotrophic cells were located in the rostral pars distalis of the pituitary. Gonadotrophic and growth hormone cells were distributed in the proximal pars distalis, but gonadotrophic cells appear also at the border of the pars intermedia. Somatolactin cells, as well as alpha-melanotrophic cells were located in the pars intermedia of B. bayad pitui-tary. The prolactin (PRL) cells were distributed in the RPD stained with orange G and showed strong immunoreactivity with antiserum to chum salmon. The adrenocorticotrophic (ACTH) cells were lead hema-toxylin-positive (PbH+) and showed strong im- mu-noreactivity with anti-human ACTH; these cells bor-dered the neurohypophysis and grouped in islets be-tween PRL cells in the RPD. Growth hormone (GH) cells were densely distributed with the gonadotrophic (GTH) cells in the PPD. They were orange G positive and reacted with antiserum to chum salmon. GTH cells were located in the central area of the PPD and in the external border of the PI. These cells were Alcyan Blue and PAS positive, and immunostained with anti-chum salmon GTH Iβ and anti-chum salmon GTH IIβ. In addition, antiserum to rat thyrotropin stimulating hormone β (TSHβ) reacted positively to the GTH cells. These results suggest that GTH I, GTH II and TSH are synthesized in the same cells in the pituitary of B. bayad. The PI was composed mainly of PbH+ cells and a PAS+ cell adjacent to the neurohypophysis. The PAS+ cells from the PI bound specifically to anti-chum somatolactin. Anti-alpha- melanin stimulating hormone (MSH) stained only the PbH+ (alpha-melanotrophic) cells of the PI.

Estradiol and GH cells: Immunohistomorphometric study in an animal model of andropause

Andropause, the culminating phase of ageing in males is characterized by the decline of the growth hormone (GH)/insulin-like growth factor 1 (IGF-1) axis that is responsible for somatic development. Estrogens on the other hand, assume a relevant somatic role, as well as the one in the pituitary. They are particularly interesting because of their therapeutic uses in certain common ageing-associated diseases. The aim of the present study was to examine the effects of subcutaneous treatment with estradiol, dipropionate on the immunohistomorphometric features of GH cells, in an animal model of the andropause. Sixteen-month-old Wistar rats were divided into sham-operated (SO), orchidectomized (Orx) and estradiol dipropionate-treated orchidectomized (Orx+Edp) groups. Estradiol dipropionate (0.625 mg/kg/day) was administered subcutaneously for three weeks while the SO and Orx groups received the vehicle alone. GH cells were identified by the peroxidase-antiperoxidase (PAP) immunohistochemical procedure. In the Orx+Edp group, GH cell volumes as well as the relative volume densities were significantly (p&lt;0.05) decreased, by 27.4% and by 61.1%, respectively, in comparison with the same parameters of SO animals. Compared to the Orx animals, the cell volumes and relative volume densities of GH cells in Orx+Edp group were also significantly (p&lt;0.05) decreased, by 23.2% and by 64.1%, respectively. It can be concluded that chronic estradiol dipropionate application in an animal in the andropause results in the suppression of immunohistochemical and morphometric parameters of pituitary GH cells.

Specific roles of Gi protein family members revealed by dissecting SST5 coupling in human pituitary cells

Despite intensive investigation over the past 20 years, the specific role played by individual G(i) protein family members in mediating complex cellular effects is still largely unclear. Therefore, we investigated the role of specific G(i) proteins in mediating somatostatin (SS) effects in somatotroph cells. Because our previous data showed that SS receptor type 5 (SST5) carrying a spontaneous R240W mutation in the third intracellular loop had a similar ability to inhibit intracellular cAMP levels to the wild-type protein but failed to mediate inhibition of growth hormone (GH) release and cell proliferation, we used this model to check specific receptor-G-protein coupling by a bioluminescent resonance energy transfer analysis. In HEK293 cells, wild-type SST5 stimulated the activation of Gα(i1-3) and Gα(oA), B, whereas R240W SST5 maintained the ability to activate Gα(i1-3) and Gα(oB), but failed to activate the splicing variant Gα(oA). To investigate the role of the selective deficit in Gα(oA) coupling, we co-transfected human adenomatous somatotrophs with SST5 and a pertussis toxin (PTX)-resistant Gα(oA) (Gα(oA(PTX-r))) protein. In PTX-treated cells, Gα(oA(PTX-r)) rescued the ability of the selective SST5 analog BIM23206 to inhibit extracellular signal-related kinase 1/2 (ERK1/2) phosphorylation, GH secretion and intracellular cAMP levels. Moreover, we demonstrated that silencing of Gα(oA) completely abolished SST5-mediated inhibitory effects on GH secretion and ERK1/2 phosphorylation, but not on cAMP levels. In conclusion, by analysing the coupling specificity of human SST5 to individual Gα(i) and Gα(o) subunits, we identified a crucial role for Gα(oA) signalling in human pituitary cells.

Cytokine-induced osteopoietic differentiation of transplanted marrow cells

AbstractTransplantation of whole bone marrow (BMT) leads to engraftment of both osteoprogenitor cells and hematopoietic cells; however, the robust osteopoietic chimerism seen early after BMT decreases with time. Using our established murine model, we demonstrate that a post-BMT regimen of either granulocyte-colony stimulating factor, growth hormone, parathyroid hormone, or stem cell factor each stimulates greater donor osteoblast chimerism at 4 months posttransplantation than saline-treated controls and approximates the robust osteopoietic chimerism seen early after BMT; however, only growth hormone led to significantly more donor-derived osteocytes than controls. Importantly, there were no adverse hematologic consequences of the different treatments. Our data demonstrate that these cytokines can stimulate the differentiation of transplanted donor marrow cells into the osteopoietic lineage after BMT. Post-BMT cytokine therapy may generate durable osteopoietic engraftment, which should lead to sustained clinical benefit and render BMT more applicable to bone disorders.

Transgenic mice expressing the human growth hormone gene provide a model system to study human growth hormone synthesis and secretion in non-tumor-derived pituitary cells: Differential effects of dexamethasone and thyroid hormone

Growth hormone (GH) is regulated by pituitary and hypothalamic factors as well as peripheral endocrine factors including glucocorticoids and thyroid hormone. Studies on human GH are limited largely to the assessment of plasma levels in endocrine disorders. Thus, insight into the regulation of synthesis versus secretion has come mainly from studies done on non-human GH and/or pituitary tumor cells. However, primate and non-primate GH gene loci have differences in their structure and, by extension, regulation. We generated transgenic (171hGH/CS-TG) mice containing the intact hGH1 gene and locus control region, including sequences required for integration-independent and preferential pituitary expression. Here, we show hGH co-localizes with mouse (m) GH in somatotrophs in situ and in primary pituitary cells. Dexamethasone treatment increased hGH and mGH, as well as GH releasing hormone (GHRH) receptor RNA levels, and hGH release was stimulated by GHRH treatment. By contrast, triiodothyronine decreased or had no effect on hGH and mGH production, respectively, and the negative effect on hGH was also seen in the presence of dexamethasone. Thus, 171hGH/CS-TG mouse pituitary cultures represent a model system to investigate hormonal control of hGH synthesis and secretion.

Prolactin-cell adenoma with signet-ring cells: a case report

Signet-ring cell changes in the pituitary adenomas are extremely rare. To date, there have been only two reports documenting signet-ring cells in pituitary adenomas, one in a growth-hormone cell adenoma and the other in a nullcell adenoma. This report describes, for the first time, signet-ring cells in a prolactincell adenoma. The patient is a 46-year-old male who presented with severe headache and acute on chronic visual loss. Radiographic studies demonstrated a large cystic pituitary lesion with evidence of pituitary apoplexy. Laboratory values were consistent with a prolactin-cell adenoma. The patient underwent transsphenoidal resection of the prolactin-cell adenoma with significant post-operative improvement. The tumor was composed of sheets of monomorphic round cells with conspicuous nuclei and granular cytoplasm, consistent with pituitary adenoma. Many cells had eccentric, often crescentic-shaped nuclei, imparting a signet-ring appearance and immunostaining was positive for prolactin, denoting an atypical prolactin-cell adenoma. The MIB-1 labeling index was slightly elevated. Electron microscopy demonstrated the presence of vacuolated areas in the cytoplasm that were not membrane bound and did not have specific inclusions. This case augments the literature on pituitary adenomas with signet-ring cells. The clinical significance of signet-ring cells in pituitary adenomas is unknown. Accumulation of clinical cases, together with the advances in molecular techniques and experimental models, may yield further insight.

The Insulin-Like Growth Factor I (IGF-I) Within the Bony Fish Pituitary: New Morphofunctional and Phylogenetic Aspects

IGF-I is a major hormonal regulator of differentiation, growth, proliferation, and development. It is mainly produced in the liver, the principal source of endocrine IGF-I. The main stimulus for synthesis and release of liver IGF-I is growth hormone (GH) from the anterior pituitary, and IGF-I specifically inhibits GH gene transcription and secretion via a negative feedback mechanism. As shown for species throughout phylogeny, IGF-I is also produced in extrahepatic sites, including the pituitary, and very recently, new insights have been achieved into the distinct localization of IGF-I. Bony fish pituitary preserves the embryonic compartmentalization throughout life, thus, each endocrine cell type is situated in a distinct region. This makes fish pituitary an excellent tool for morphologic investigations. IGF-I mRNA and/or peptide has been located to subtypes of endocrine cells with similar distribution patterns in lower and higher vertebrates suggesting highly conserved and, thus, important physiological roles of intrapituitary IGF-I. Since a major task of IGF-I is to prevent apoptosis and promote cell proliferation, IGF-I released from the endocrine adenohypophyseal cells may have protective and proliferative autocrine and/or paracrine effects. This is supported by the presence of the type 1 IGF receptor (IGF-1R) at all endocrine subpopulations as has been shown in rat and by the constitutive presence of IGF-I in ACTH cells in bony fish and mammals. ACTH cells probably are challenged in stressful situations by pro-apoptotic cytokines and hormones, and might, thus, have a special demand for IGF-I. The increased transient expression of IGF-I in gonadotrophs during puberty, and in subordinate males of tilapia suggests an impact in sexual differentiation and maturation, a question which has been recently underlined to be of major importance. The pronounced inter-individual differences in the IGF-I content of the GH cells may indicate that synthesis and release of IGF-I from GH cells depend on the physiological status, most likely the serum IGF-I level. Further studies should be performed to elucidate these morphofunctional observations.

Molecular Cloning and Expression Analysis of Porcine Ghrelin O-Acyltransferase

The peptide hormone ghrelin is secreted in the stomach, with unique N-octanoylation at serine 3, which is a requirement for its functionality. These functions include growth hormone release, appetite stimulation, gastrointestinal motility, glucose regulation, and cell proliferation. The enzyme responsible for ghrelin acylation was recently identified as ghrelin O-acyltransferase (GOAT). In this study, porcine GOAT was cloned and characterized. A full-length cDNA of GOAT of 2013 bp was obtained, which included a 70-bp 5' UTR, a 635-bp 3' UTR, and a 1308-bp open reading frame encoding a protein of 415 amino acids. The GOAT and ghrelin mRNAs are co-expressed in stomach, pancreas, and duodenum at high levels. GOAT was also detected in liver, lung, brain, testis, spleen, kidney, heart, muscle, lipid, and ovary. Our results provide an important basis for further research on GOAT function and the relationship between ghrelin and GOAT.

DIFFERENTIAL INVOLVEMENT OF PKC AND PKA IN GHRELIN-INDUCED GROWTH HORMONE AND GONADOTROPIN RELEASE FROM PRIMARY CULTURES OF DISPERSED GOLDFISH PITUITARY CELLS.

Event Abstract Back to Event DIFFERENTIAL INVOLVEMENT OF PKC AND PKA IN GHRELIN-INDUCED GROWTH HORMONE AND GONADOTROPIN RELEASE FROM PRIMARY CULTURES OF DISPERSED GOLDFISH PITUITARY CELLS. Caleb L. Grey1 and John P. Chang1* 1 University of Alberta, Biological Sciences, Canada Ghrelin (GRLN) stimulates feeding and the release of pituitary growth hormone (GH) and maturational gonadotropin (LH) in goldfish, thus providing a possible link between energy balance and reproduction. Previous work shows that mRNAs for GRLN and its receptors are expressed in the goldfish pituitary. Extracellular Ca2+ entry through L-type voltage-sensitive Ca2+ channels and increases in intracellular Ca2+ are important signaling components leading to goldfish (g)GRLN19-elicited GH and LH release. In this study, we examined the role of protein kinase C (PKC) and A (PKA) in gGRLN19-induced hormone secretion via column perifusion of dispersed goldfish pituitary cells, and single cell Ca2+-imaging of identified goldfish somatotropes and gonadotropes. PKC inhibitors (bisindolylmaleimide-II and Gö 6976) attenuated gGRLN19-stimulated hormone secretion and associated Ca2+ signals. gGRLN19-induced hormone release and Ca2+ signals were not observed when cells were already stimulated by a PKC agonist (DiC8). PKA inhibitors (H-89 and KT5720), however, only inhibited gGRLN19-induced hormone release and Ca2+ responses in LH cells. On the other hand, an adenylate cyclase activator (forskolin) enhanced gGRLN19-induced GH, but not LH, release. Ca2+ signals elicited by combined forskolin and gGRLN19 treatment were not different from those to either treatment alone in either cell type. These results suggest that while PKC and PKA mediate GRLN actions on LH release by actions upstream of Ca2+ signals, similar responses in GH cells only involve PKC. In addition, activation of PKA may enhance GRLN-stimulated GH secretion by actions downstream of Ca2+ changes. (Supported by NSERC.) Acknowledgements NSERC University of Alberta, Biological Sciences Province of Alberta Keywords: calcium imaging, Goldfish ghrelin, Goldfish pituitary, identified gonadotropes, identified somatotropes, perifusion, PKA, PKC Conference: NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology, Ann Arbor, United States, 13 Jul - 16 Jul, 2011. Presentation Type: Oral Presentation Topic: Neuroendocrine control of reproduction Citation: Grey CL and Chang JP (2011). DIFFERENTIAL INVOLVEMENT OF PKC AND PKA IN GHRELIN-INDUCED GROWTH HORMONE AND GONADOTROPIN RELEASE FROM PRIMARY CULTURES OF DISPERSED GOLDFISH PITUITARY CELLS.. Front. Endocrinol. Conference Abstract: NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology. doi: 10.3389/conf.fendo.2011.04.00135 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 22 Jul 2011; Published Online: 09 Aug 2011. * Correspondence: Dr. John P Chang, University of Alberta, Biological Sciences, Edmonton, Canada, john.chang@ualberta.ca Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Caleb L Grey John P Chang Google Caleb L Grey John P Chang Google Scholar Caleb L Grey John P Chang PubMed Caleb L Grey John P Chang Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.