Induction of growth hormone release by glycyrrhizae radix on rat

Induction of growth hormone (GH) by Glycyrrhizae Radix (GR), one of the most popular herbal medicine, and its major ingredients were studied in rat pituitary cells in vitro and in vivo assay. The MeOH extract and the n-hexane (HX) fraction of GR induced rat GH (rGH) release up to 1.89 times (0.34 +/- 0.04 nM) and 4.59 times (0.83 +/- 0.03 nM), compared to the basal level (p < 0.05). Among many ingredients isolated and purified from GR both glycyrrhetinic acid and glycyrrhizin induced significantly rGH release compared to the control (p < 0.05). After an intravenous injection of rat growth hormone releasing hormone (rGHRH) (10 microg/kg) as positive control, in SD rats, Tmax of plasma rGH level was 10 min, C(max) was 3.84 +/- 0.01 nM (n = 3), and enhanced plasma rGH level returned to the baseline in 90 min. Both AUC(0-90) (area under the curve) of plasma rGH level after HX fraction and that after rGHRH administration were increased significantly from the basal level, respectively (p < 0.01). In conclusions, HX fraction is the most active fraction of MeOH extract of GR in rGH induction.     

N-(2-hydroxy phenyl) acetamide: a novel suppressor of Toll-like receptors (TLR-2 and TLR-4) in adjuvant-induced arthritic rats

This study investigated the roles of Ras, ERK, and Akt in the glucocorticoid-induced differentiation of growth hormone-producing pituitary cells in vitro. Pituicytes isolated from day-18 rat embryos were cultured with 50 mM dexamethasone in addition to specific inhibitors of Ras (manumycin; 0.5, 5, 50 nM), ERK (U0126, 10 μM), or Akt (LY294002, 25 μM). Differentiation was assessed using immunofluorescent staining of intracellular growth hormone. Radioimmunoassay and Western blot analyses were used to determine levels of secreted and intracellular growth hormone, respectively. Manumycin reduced the fraction of growth hormone-positive cells and dexamethasone-induced growth hormone secretion in a dose-dependent manner (both P < 0.001). In the absence of dexamethasone, LY294002 and U0126 did not alter the fraction of growth hormone-positive cells or intracellular growth hormone protein expression or secretion. Both LY294002 and U0126 alone significantly attenuated the fraction of dexamethasone-treated GH-positive cells and the secretion of GH compared to those of cells treated only with dexamethasone (50 nM for 44 h or 48 h) (all P < 0.05). Dexamethasone treatment alone did not change GH protein levels. Treatment of cells with a combination of LY294402 and U0126 significantly attenuated the fraction of dexamethasone-treated GH-positive cells, GH protein levels, and GH secretion compared to cells treated with dexamethasone alone (all P < 0.05). Moreover, dexamethasone-induced phosphorylation of GTP-Ras, ERK, and Akt was significantly attenuated by exposure to the respective inhibitors (P < 0.05). Taken together, our results indicate that Ras, ERK, and Akt are key effectors in the glucocorticoid-induced differentiation of growth hormone-secreting cells.     

Hormonal regulation of sodium/sulfate co-transport in renal epithelial cells

Serum sulfate concentrations are elevated in infants, young children, and pregnant women due, at least in part, to increased renal sulfate reabsorption. Little is known about the effects of hormones, particularly those involved in growth, development, and pregnancy, on renal sulfate reabsorption. The objective of this investigation was to examine the effects of growth hormone (GH), insulin-like growth factor 1 (IGF-1), progesterone (PG), and 17beta-estradiol (EST) on renal sodium/sulfate co-transport. 35S-sulfate uptake was determined in Madin-Darby canine kidney (MDCK)/NaSi-1 cells (MDCK cells that have been stably transfected with rat sodium/sulfate co-transporter (NaSi-1) cDNA) and in opossum kidney (OK) cells. NaSi-1 mRNA was determined by RT-PCR and protein levels by ELISA. GH (0.1 nM) significantly increased the sodium/sulfate co-transport in MDCK/NaSi-1 cells up to 35%. IGF-1 induced a concentration-related stimulation of the sodium/sulfate co-transport with a maximal response observed at 1000 nM (59% increase). Sodium-dependent sulfate uptake was significantly increased when cells were preincubated with 10 nM PG, 10 nM EST, or 10 nM PG/10 nM EST up to 41%, 46%, or 39%, respectively. OK cells exhibited endogenous sodium-dependent sulfate transport; significantly increased sodium/sulfate co-transport was also observed in OK cells that were preincubated with GH, IGF-1, and PG/EST, although not with EST alone. The NaSi-1 mRNA and NaSi-1 protein levels were significantly increased in MDCK/NaSi-1 cells treated with 0.1 nM GH, 100 nM IGF-1, 10 nM PG, and/or 10 nM EST compared with control. These results suggest that the increased renal sulfate reabsorption that occurs in neonates, young and pregnant humans, and animals could be mediated by the increased steady-state levels of NaSi-1 mRNA produced by the higher plasma concentrations of GH, IGF-1, or PG/EST.     

GH重组蛋白对达氏鲟生长、血液生化和体组成的影响

为研究生长激素（GH）重组蛋白对达氏鲟生长、代谢及鱼体肝组分的影响,构建了GH成熟肽融合原核表达载体pET32a-AdGH,并将其在宿主菌BL21（DE3）中诱导表达,重组蛋白rAdGH以包涵体的形式存在。设置了4个试验组,分别在鲟鱼商品饲料中添加含量为0（对照组）、10（低处理组）、50（中处理组）和100 mg/kg（高处理组）的粉状rAdGH,连续投喂8周。结果表明,低水平rAdGH添加能够显著促进鱼体生长,提高特定生长率,降低饵料系数,提高肝体比和脏体比;进一步的分析表明,低水平rAdGH添加可提高除血糖外所有测定的血液指标数值,反映了机体代谢水平的增强。各浓度rAdGH的添加均能提高鱼体肝和肌肉中蛋白质、水分含量,降低脂肪含量。rAdGH对鱼体生长和代谢的影响可能与其剂量相关,低水平的添加可显著增强鱼体代谢水平,加快肝中蛋白质的沉积与脂肪的消耗,促进鱼体生长;高水平的添加进一步增强其代谢水平,但其促生长的功能下降,部分血液指标异常,肝组分异常,疑似肝损伤。研究探索了鲟鱼重组生长激素的生长调控功能,为重组生长激素在鲟鱼养殖中的应用提供了基础。     

Melanin-concentrating hormone stimulates human growth hormone secretion: a novel effect of MCH on the hypothalamic-pituitary axis

Melanin-concentrating hormone (MCH), a 19-amino acid orexigenic (appetite-stimulating) hypothalamic peptide, is an important regulator of energy homeostasis. It is cleaved from its precursor prepro-MCH (ppMCH) along with several other neuropeptides whose roles are not fully defined. Because pituitary hormones such as growth hormone (GH), ACTH, and thyroid-stimulating hormone affect body weight and composition, appetite, insulin sensitivity, and lipoprotein metabolism, we investigated whether MCH exerts direct effects on the human pituitary to regulate energy balance using dispersed human fetal pituitaries (21-22 wk gestation) and cultured GH-secreting adenomas. We found that MCH receptor-1 (MCH-R1), but not MCH receptor-2, is expressed in both normal (fetal and adult) human pituitary tissues and in GH cell adenomas. MCH (10 nM) stimulated GH release from human fetal pituitary cultures by up to 62% during a 4-h incubation (P < 0.05). Interestingly, neuropeptide EI (10 nM), which is also cleaved from ppMCH, increased human GH secretion by up to 124% in fetal pituitaries. A milder, albeit significant, induction of GH secretion by MCH (20%) was seen in cultured GH-secreting pituitary adenomas. A comparable stimulation of GH secretion was seen when cultured mouse pituitary cells were treated with MCH. Treatment of cultured GH adenoma cells with MCH (100 nM) induced extracellular signal-regulated kinases 1 and 2 phosphorylation, suggesting activation of MCH-R1. In aggregate, these data suggest that MCH may regulate pituitary GH secretion and imply a potential cross-talk mechanism between appetite-regulating neuropeptides and pituitary hormones.     

Effect of gonadotropin-releasing hormone on phagocytic leucocytes of rainbow trout

To clarify the role of gonadotropin-releasing hormone (GnRH) in the fish immune system, in vitro effect of GnRH was examined in phagocytic leucocytes of rainbow trout (Oncorhynchus mykiss). Gene expression of GnRH-receptor was detected by RT-PCR in leucocytes from head kidney. Administration of sGnRH increased proliferation and mRNA levels of a proinflammatory cytokine, tumor necrosis factor (TNF)-α, in trout leucocytes. Superoxide production in zymosan-stimulated phagocytic leucocytes was also increased by sGnRH in a dose-related manner from 0.01 to 100 nM. There was no significant effect of sGnRH on mRNA levels of growth hormone (GH) expressed in trout phagocytic leucocytes. Immunoneutralization of GH by addition of anti-salmon GH serum into the medium could not block the stimulatory effect of sGnRH on superoxide production. These results indicate that GnRH stimulates phagocytosis in fish leucocytes through a GnRH-receptor-dependent pathway, and that the effect of GnRH is not mediated through paracrine GH in leucocytes.     

Production of a biologically active growth hormone from giant catfish (Pangasianodon gigas) in Escherichia coli

Giant catfish growth hormone (gcGH) cDNA was cloned and expressed in E. coli. The expected 20.5 kDa protein corresponded to the mature gcGH and was efficiently expressed. This protein was produced as inclusion bodies and comprised about 20% of total cellular proteins. The recombinant hormone promoted growth when injected intramuscularly or intraperitoneally into goldfish (Carassius auratus) at 0.1 or 1 microg soluble gcGH per g fish body wt per week. In addition, the recombinant gcGH inclusions had growth-promoting activity similar to that of the soluble form when the fish was received either by intraperitoneal injection or by oral administration.     

Dihydropyridine modulators of voltage-sensitive Ca2+ channels specifically regulate prolactin production by GH4C1 pituitary tumor cells

To determine whether hormone synthesis by the GH4C1 pituitary cell line could be regulated by specifically modulating the movement of Ca2+ through voltage-sensitive channels, we have compared the effects of the dihydropyridine Ca2+ channel agonist BAY K8644 and the antagonist nimodipine on hormone production and Ca2+ current in these cells. BAY K8644 elicited, after a 10-15-h lag, a dose-dependent increase in prolactin (PRL) production as determined by measurements of total intracellular and secreted hormone. Over a 72-h period, GH4C1 cells incubated with 300 nM BAY K8644 produced 2-3 times as much total PRL as control cells. The effect on PRL was specific, since BAY K8644 did not increase growth hormone production, cell growth rate, or total cell protein. Exposing GH4C1 cells to BAY K8644 for short periods, up to 90 min, did not induce the delayed increase in PRL production observed with longer incubations. The effects of nimodipine were opposite to those of the Ca2+ channel agonist. PRL production was reduced 85% during 48-h treatment with 200 nM nimodipine, whereas growth hormone production was decreased less than 15%, and cell growth and total protein were unaffected. The actions of these two drugs on PRL production were well correlated with their effects on GH4C1 Ca2+ currents as measured by whole-cell patch-clamp recordings. BAY K8644 enhanced the magnitude of the peak Ca2+ current and shifted the current-voltage relationship such that Ca2+ channels were activated at less depolarized potentials. Nimodipine potently inhibited Ca2+ movement through the non-inactivating channel, while it antagonized the increases elicited by BAY K8644. These results indicate that PRL synthesis by GH4C1 cells can be specifically regulated by agents that enhance or block the movement of Ca2+ through voltage-sensitive channels. They also suggest that hormone synthesis by a secretory cell may be coupled to electrical activity by the opening of Ca2+ channels.     

Growth hormone binding and stimulation of amino acid uptake in epithelial cells of rat ventral prostate

The binding of [125I]-human growth hormone (hGH) was studied in epithelial cells isolated from rat ventral prostate. Binding and degradation were dependent on time and temperature. The effect of a lysosomotropic agent suggested internalization and lysosomal degradation of the hormone. Dissociation and stoichiometric studies indicated the existence of a single class of GH receptors with a Kd of 0.7 nM and a binding capacity of 46 fmol hGH bound mg-1 cell protein. The receptor appeared to possess a somatotrophic nature since lactogenic hormones such as human placental lactogen and rat prolactin exhibited a very low degree of competition (whereas a variety of unrelated hormones and neuropeptides showed no effect). GH-stimulated leucine uptake by the cells in a time- and dose-dependent manner, half maximal effect being observed at 0.32 nM GH thus suggesting a direct relationship with the binding step.     

Actions of L-363,586, a cyclic hexapeptide analogue of somatostatin, on GH secretion by human somatotrophinoma cells in vitro.

L-363,586 is a cyclic, hexapeptide analogue of somatostatin-14 with potent inhibitory actions on rat growth hormone (GH) release in vitro. The studies reported here investigate the direct effects of L-363,586 on basal and growth hormone-releasing factor (GRF)-stimulated GH secretion from 3 human somatotrophinomas in dispersed cell culture. 1nM and 10nM L-363,586 inhibited both basal and GRF-stimulated GH release from cells of all 3 somatotrophinomas during a 2h treatment period, whilst 100nM L-363,586 had a prolonged inhibitory action on basal GH secretion from cells of 2 of the tumours throughout treatment and recovery periods. Rebound release of GH was observed with cells of 1 tumour following treatment with L-363,586 plus GRF. The actions of L-363,586 were similar to those of somatostatin-14. These data suggest that L-363,586 may have a role in the treatment of acromegaly.     

Growth hormone gene regulation: a paradigm for cell-type-specific gene activation

The growth hormone (GH) gene is specifically expressed within specialized cells of the anterior pituitary. The central role in GH gene activation is played by GHF-1, a homeodomain protein that is itself specifically expressed in the anterior pituitary.     

Chimeric bovine-human growth hormone prepared by recombinant DNA technology: binding properties and biological activity

A chimeric bovine GH (amino acids Met-Asp-Gln-greater than 1-23) and human GH (hGH) (amino acids 24-191) plasmid was constructed and expressed in Escherichia coli. The purified protein (chimeric GH) exhibited a 2-3 order of magnitude lower affinity toward lactogenic receptors in Nb2 lymphoma cells, microsomal fractions from bovine mammary gland and male rat liver. The affinity towards somatogenic receptors in IM-9 human lymphocytes and male rat liver was decreased to a much lesser degree. This diminished affinity towards lactogenic receptors was accompanied by a parallel decrease in the ability of the chimeric GH to stimulate proliferation of Nb2-11C lymphoma cells and the lipogenesis in bovine mammary gland. This implies that occupation of the respective receptors by either chimeric GH or hGH leads to identical postreceptoral effects. The chimeric GH was also capable of down-regulating the lactogenic receptors in Nb2 lymphoma cells and was recognized by three anti-hGH monoclonal antibodies. These and previously published results indicate that the N-terminal part of hGH is essential for the high affinity binding to lactogenic receptors and subsequent biological effect. Removal or replacement by a corresponding part of bovine GH converts the hormone, respectively to weak antagonist or agonists. Analysis of our data, based on hydropathy index leads us to suggest that the high affinity binding site of the hGH towards lactogenic receptors is mainly confined to amino acids nos. 8-18.     

鲤鱼(Cyprinus carpio)生长激素基因克隆及原核表达

采用逆转录—聚合酶链式反应（ＲＴ－ＰＣＲ）方法,从鲤鱼脑垂体总ＲＮＡ中扩增出编码鲤鱼生长激素（ＧＨ）成熟肽基因序列．定向克隆至质粒ｐＵＣ１８,克隆的鲤鱼ＧＨｃＤＮＡ不含信号肽序列并以新的起始密码子ＡＴＧ取代鲤鱼ＧＨｃＤＮＡ第１个密码子ＴＣＡ．序列分析表明,与Ｋｏｒｅｎ报道的鲤鱼ＧＨｃＤＮＡ相比有两个碱基差异,但推断的氨基酸序列完全一致．将鲤鱼ＧＨｃＤＮＡ定向克隆至原核表达载体ｐＢＶ２２０,构建成重组鲤鱼ＧＨ基因表达载体ｐＢＶｃＧＨ８．ＳＤＳ－ＰＡＧＥ和薄层扫描分析表明：经４２℃诱导,ｐＢＶｃＧＨ８在大肠杆菌中可表达一分子量约２２０００的特异蛋白,表达量占细胞总蛋白的２９．２％．该基因重组的鲤鱼ＧＨ添加到饲料中投喂罗非鱼,证实有明显的促进生长作用