scholarly journals Enhanced Pulsatile Growth Hormone Secretion and Altered Metabolic Hormones by in Vivo Hexarelin Treatment in Streptozotocin-Induced Diabetic Rats

2018 ◽  
Vol 19 (10) ◽  
pp. 3067 ◽  
Author(s):  
Xinli Zhang ◽  
Jin-Kui Yang ◽  
Chen Chen
Keyword(s):  
Growth Hormone ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Diabetic Animal ◽  
Diabetic Rats ◽  
Control Group ◽  
Beneficial Effects ◽  
Gh Secretion ◽  
Fasting Level

Significant growth hormone (GH) reductions have been reported in diabetic animal models with disturbed metabolic balance coinciding with GH deficiency. Therefore, enhanced GH secretion may have beneficial effects in controlling diabetes. Thus, we aim to investigate the effect of hexarelin, a synthetic GH secretagogue (GHS), on GH secretion in streptozotocin (STZ, 65 mg/kg)-induced diabetic rats. Daily hexarelin (100 μg/kg) treatment was performed for two weeks in four-week-long STZ-diabetic and vehicle control rats. Pulsatile GH secretion in STZ-rats was significantly reduced in total, pulsatile, basal, and mass of GH secretion per burst. In addition, impaired GH secretion was followed by an increase in fasting-level free fatty acids (FFAs) and a decrease in insulin-like growth factor 1 (IGF-1) compared to control rats. After hexarelin treatment, pulsatile GH secretion in STZ-rats was significantly increased in total, pulsatile, and basal, but not in the mass GH secretion per burst, compared to STZ-rats without hexarelin treatment. However, there was no significant elevation in GH secretion in the hexarelin-treated control group. In addition, hexarelin-treated STZ-rats showed a significant decrease in fasting level FFAs, whereas suppression of fasting level for IGF-1 was maintained. These results suggest that STZ-induced diabetic rats have impaired pulsatile GH secretion, causing increased FFAs and decreased IGF-1 levels in circulation. Hexarelin injections for two weeks is able to normalize impaired pulsatile GH secretion with normal fasting levels of FFAs, but fails to recover IGF-1 levels.

A possible relationship between serum transferrin, growth hormone secretion and height velocity in children

1980 ◽  
Vol 93 (2) ◽  
pp. 134-138 ◽  
Author(s):  
M. Donnadieu ◽  
R. M. Schimpff ◽  
P. Garnier ◽  
J. L. Chaussain ◽  
J. C. Job
Keyword(s):  
Growth Hormone ◽  
Growth Regulation ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Height Velocity ◽  
Obese Children ◽  
Gh Secretion ◽  
Growth Promoting

Abstract. Since transferrin (Tf) in vitro has a growth-promoting activity and is associated with NSILA properties, the aim of this work was to study in vivo the relationships between Tf, somatomedin activity (SM), growth hormone (GH) secretion, and height velocity in children. An iv infusion of ornithine hydrochloride was given to 23 controls; the induced rise of GH was accompanied by a simultaneous fall of SM (r = −0.711, P < 0.001) and was preceded by a fall of Tf (r = −0.610, P < 0.01). In 17 obese children SM was within the normal range, when Tf levels were higher and arginineinduced GH peaks lower than in the controls, and a negative correlation was found between Tf basal levels and GH peaks (r = −0.608, P < 0.01). In 9 children with confirmed hypopituitarism the Tf levels were significantly lower than in the controls. In 14 children with confirmed or suspected hypopituitarism a single im injection of hGH (6 mg) failed to induce Tf variations over 24 h. In 39 of these children the height velocity was significantly correlated with Tf basal levels (r = 0.701, P < 0.001). These data suggest that transferrin is involved in growth regulation, and that GH secretion is related to transferrin levels by a feed-back mechanism.

Glucocorticoid modulation of growth hormone secretion in vitro. Evidence for a biphasic effect on GH-releasing hormone mediated release

1987 ◽  
Vol 114 (4) ◽  
pp. 465-469 ◽  
Author(s):  
Gian Paolo Ceda ◽  
Robert G. Davis ◽  
Andrew R. Hoffman
Keyword(s):  
Growth Hormone ◽  
Prolonged Exposure ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Inhibitory Effect ◽  
Pituitary Cells ◽  
Gh Secretion ◽  
Glucocorticoid Action

Abstract. Glucocorticoids have been shown to have both stimulatory and suppressive effects on GH secretion in vitro and in vivo. In order to study the kinetics of glucocorticoid action on the somatotrope, cultured rat pituitary cells were exposed to dexamethasone for varying periods of time. During short-term incubations (≤ 4 h), dexamethasone inhibited GHRH and forskolin-elicited GH secretion, but during longer incubation periods, the glucocorticoid enhanced both basal and GHRH-stimulated GH release. The inhibitory effect of brief dexamethasone exposure was also seen in cells which previously had been exposed to dexamethasone. In addition, growth hormone secretion from cultured rat and human somatotropinoma cells was inhibited by a brief exposure to dexamethasone. Thus, the nature of glucocorticoid action on the isolated cultured somatotrope is biphasic, with brief exposure inhibiting, and more prolonged exposure stimulating GH secretion.

Growth hormone-releasing factor-induced growth hormone secretion from perifused rat anterior pituitary cells: lack of influence of glucose concentration, and normal responses in pituitary cells from diabetic animals

1989 ◽  
Vol 122 (3) ◽  
pp. 657-660 ◽  
Author(s):  
G. Caldwell ◽  
G. Hart ◽  
E. M. Kohner ◽  
J. M. Burrin
Keyword(s):  
Growth Hormone ◽  
Anterior Pituitary ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Initial Response ◽  
Diabetic Rats ◽  
Pituitary Cells ◽  
Gh Secretion ◽  
Anterior Pituitary Cells ◽  
Streptozotocin Induced Diabetes

ABSTRACT The mechanism responsible for the suppression of GH secretion in hyperglycaemia and hypoglyceamia in rats has been investigated using perifusion of anterior pituitary cells. When perifused with Krebs-Ringer bicarbonate containing normal (5 mmol/l), high (20 mmol/l) and low (1 mmol/l) concentrations of glucose, the GH responses to GH-releasing factor (GRF) were 85 ± 5, 85·5 ± 5·4 and 89 ± 3·0 (s.e.m.)% respectively compared with the initial response to GRF at 5 mmol/l in each column. The mean GH response to GRF from anterior pituitary cells of normal rats was 6·58 ± 0·88 μg/three pituitaries, which was not statistically different from that of cells from rats with streptozotocin-induced diabetes (5·40 ± 0·68 μg/three pituitaries). It is concluded that GH suppression in diabetic rats and during hypoglycaemia is not mediated by changes in the GH response to GRF. Journal of Endocrinology (1989) 122, 657–660

Stimulation of in-vivo growth hormone secretion in young chickens by rat hypothalamic growth hormone-releasing factor and synthetic analogues

1986 ◽  
Vol 108 (3) ◽  
pp. 413-416 ◽  
Author(s):  
C. G. Scanes ◽  
S. Harvey ◽  
J. Rivier ◽  
W. Vale
Keyword(s):  
Growth Hormone ◽  
Domestic Fowl ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Gh Secretion ◽  
Structure Activity ◽  
In Vivo Growth ◽  
Plasma Gh ◽  
Stimulation Of

ABSTRACT Rat hypothalamic GH-releasing factor (rhGRF), at doses between 0·1 and 10 μg/kg, increased plasma GH concentrations in immature domestic fowl 5–10 min after i.v. injection. Sodium pentobarbitone anaesthesia blunted the GH responses to rhGRF, although in both conscious and anaesthetized chicks the maximal responses were induced by a dose of 1 μg rhGRF/kg. The stimulatory effect of rhGRF on in-vivo GH secretion was less than that provoked by corresponding doses of human pancreatic GRF, but greater than that elicited by two rhGRF analogues, (Nle27)-rhGRF(1–32) and (Nle27)-rhGRF(1–29). These results demonstrate that the chicken pituitary is responsive to mammalian GRF and provide evidence of structure-activity relationships of GRF in the domestic fowl. J. Endocr. (1986) 108, 413–416

EFFECT OF CHICKEN HYPOTHALAMUS ON PROLACTIN AND GROWTH HORMONE SECRETION IN MALE CHICKENS

1979 ◽  
Vol 82 (2) ◽  
pp. 193-197 ◽  
Author(s):  
S. HARVEY ◽  
C. G. SCANES ◽  
A. CHADWICK ◽  
G. BORDER ◽  
N. J. BOLTON
Keyword(s):  
Growth Hormone ◽  
Medulla Oblongata ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Pituitary Cells ◽  
Plasma Prolactin ◽  
Gh Secretion ◽  
Brain Tissues

SUMMARY The effects of a chicken hypothalamic extract (HE) on the secretion of prolactin and growth hormone (GH) in vivo have been investigated by radioimmunoassay in the domestic fowl. Different i.v. doses of HE (0·25–25 HE equivalents/kg body weight) had no effect on GH secretion in conscious or anaesthetized cockerels. In both groups of birds the concentration of plasma prolactin was significantly increased within 10 min of administration of the extract. Extracts of other brain tissues (cerebral cortex, cerebellum and medulla oblongata) had no stimulatory effect on prolactin or GH secretion. Release of both prolactin and GH by dispersed pituitary cells and by hemipituitary glands in vitro was enhanced following incubation with HE (5 hypothalami equivalents/ml) or with single whole hypothalami respectively. Other brain tissues (cerebellum, optic lobes and medulla oblongata) had no effect on the concentration of prolactin or GH released by incubated hemipituitary glands.

Deterministic construct of amplifying actions of ghrelin on pulsatile growth hormone secretion

2005 ◽  
Vol 288 (6) ◽  
pp. R1649-R1663 ◽  
Author(s):  
Leon S. Farhy ◽  
Johannes D. Veldhuis
Keyword(s):  
Growth Hormone ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Physiological Data ◽  
Female Rat ◽  
Growth Hormone Secretagogue ◽  
Gh Secretion ◽  
Ensemble Effects ◽  
Ghs Receptor

Ghrelin is a native ligand for the growth hormone secretagogue (GHS) receptor that stimulates pulsatile GH secretion markedly. At present, no formal construct exists to unify ensemble effects of ghrelin, GH-releasing hormone (GHRH), somatostatin (SRIF), and GH feedback. To model such interactions, we have assumed that ghrelin can stimulate pituitary GH secretion directly, antagonize inhibition of pituitary GH release by SRIF, oppose suppression of GHRH neurons in the arcuate nucleus (ArC) by SRIF, and induce GHRH secretion from ArC. The dynamics of such connectivity yield self-renewable GH pulse patterns mirroring those in the adult male and female rat and explicate the following key experimental observations. 1) Constant GHS infusion stimulates pulsatile GH secretion. 2) GHS and GHRH display synergy in vivo. 3) A systemic pulse of GHS stimulates GH secretion in the female rat at any time and in the male more during a spontaneous peak than during a trough. 4) Transgenetic silencing of the neuronal GHS receptor blunts GH pulses in the female. 5) Intracerebroventricular administration of GHS induces GH secretion. The minimal construct of GHS-GHRH-SRIF-GH interactions should aid in integrating physiological data, testing regulatory hypotheses, and forecasting innovative experiments.

Acipimox enhances spontaneous growth hormone secretion in obese women

2004 ◽  
Vol 286 (4) ◽  
pp. R693-R698 ◽  
Author(s):  
Petra Kok ◽  
Madelon M. Buijs ◽  
Simon W. Kok ◽  
Inge H. A. P. van Ierssel ◽  
Marijke Frölich ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Normal Weight ◽  
Control Group ◽  
Time Interval ◽  
Obese Women ◽  
Double Blind ◽  
Deconvolution Analysis ◽  
Gh Secretion

We hypothesized that a high circulating free fatty acid (FFA) concentration is involved in the pathogenesis of hyposomatotropism associated with obesity. To evaluate this hypothesis, 10 healthy premenopausal women (body mass index 33.8 ± 1.0 kg/m2) were studied in the follicular phase of their menstrual cycle at two occasions with a time interval of at least 8 wk, where body weight remained stable. Subjects were randomly assigned to treatment with either acipimox (an inhibitor of lipolysis, 250 mg orally 4 times daily) or placebo in a double-blind crossover design, starting 1 day before admission until the end of the blood sampling period. Blood samples were taken during 24 h with a sampling interval of 10 min for assessment of growth hormone (GH) concentrations, and GH secretion was estimated by deconvolution analysis. Identical methodology was used to study GH secretion in a historical control group of age-matched normal weight women. GH secretion was clearly blunted in obese women (total daily release 66 ± 10 vs. lean controls: 201 ± 23 mU·lVd-1·24 h-1, P = 0.005, where lVd is liter of distribution volume). Acipimox considerably enhanced total (113 ± 50 vs. 66 ± 10 mU·lVd-1·24 h-1, P = 0.02) and pulsatile GH secretion (109 ± 49 vs. 62 ± 30 mU·lVd-1·24 h-1, P = 0.02), but GH output remained lower compared with lean controls. Further analysis did not show any relationship between the effects of acipimox on GH secretion and regional body fat distribution. In conclusion, acipimox unleashes spontaneous GH secretion in obese women. It specifically enhances GH secretory burst mass. This might mean that lowering of systemic FFA concentrations by acipimox modulates neuroendocrine mechanisms that orchestrate the activity of the somatotropic ensemble.

scholarly journals Effects of Obestatin on Energy Balance and Growth Hormone Secretion in Rodents

Endocrinology ◽  
2007 ◽  
Vol 148 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Rubén Nogueiras ◽  
Paul Pfluger ◽  
Sulay Tovar ◽  
Myrtha Arnold ◽  
Sharon Mitchell ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Energy Balance ◽  
Food Intake ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Orphan Receptor ◽  
Gh Secretion ◽  
Hypothalamic Neuropeptides

Ghrelin stimulates food intake and adiposity and thereby increases body weight (BW) in rodents after central as well as peripheral administration. Recently, it was discovered that the gene precursor of ghrelin encoded another secreted and bioactive peptide named obestatin. First reports appeared to demonstrate that this peptide requires an amidation for its biological activity and acts through the orphan receptor, GPR-39. Obestatin was shown to have actions opposite to ghrelin on food intake, BW, and gastric emptying. In the present study, we failed to observe any effect of obestatin on food intake, BW, body composition, energy expenditure, locomotor activity, respiratory quotient, or hypothalamic neuropeptides involved in energy balance regulation. In agreement with the first report, we were unable to find any effect of obestatin on GH secretion in vivo. Moreover, we were unable to find mRNA expression of GPR-39, the putative obestatin receptor, in the hypothalamus of rats. Therefore, the results presented here do not support a role of the obestatin/GPR-39 system in the regulation of energy balance.

Inhibition of growth hormone secretion by activin A in human growth hormone-secreting tumour cells

1991 ◽  
Vol 124 (6) ◽  
pp. 666-671 ◽  
Author(s):  
Masafumi Kitaoka ◽  
Kohji Takano ◽  
Yuji Tanaka ◽  
Itaru Kojima ◽  
Akira Teramoto ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Human Growth ◽  
Activin A ◽  
Tumour Cells ◽  
Free Calcium ◽  
Gh Secretion

Abstract. Effect of activin A on growth hormone secretion was studied in primary culture of 8 human GH-secreting adenomas, which were responsive to TRH in vivo. When studied in vitro, basal GH secretion was reduced in all cases when cells were pre-incubated for 48 h with activin A at a concentration of 5×10−9 mol/l or greater. Pretreatment of GH-secreting cells with 1× 10−9 mol/l activin A did not affect either basal secretion or cellular content of GH. These tumour cells also responded to TRH in vitro and the GH response to TRH was completely blocked in cells pretreated with activin A. Activin A slightly reduced the increase in cytoplasmic free calcium concentration induced by TRH. Furthermore, pretreatment of the cells with activin A attenuated GH secretion induced by A23187 or 12-O-tetradecanoyl phorbol-4-acetate, agents which bypass receptor-mediated generation of second messengers. These results indicate that activin A inhibits GH secretion by directly acting on human GH-secreting cells and that activin A inhibits the action of TRH by acting on multiple steps in the messenger system.

Secretory bursts of growth hormone secretion in the dog may be initiated by somatostatin withdrawal

1984 ◽  
Vol 62 (2) ◽  
pp. 199-207 ◽  
Author(s):  
John S. Cowan ◽  
Penney Gaul ◽  
Bruce C. Moor ◽  
Jacob Kraicer
Keyword(s):  
Growth Hormone ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Metabolic Clearance ◽  
Time Data ◽  
Basal Secretion ◽  
Gh Secretion ◽  
Plasma Gh ◽  
Secretion Rates

In 28 6-h experiments on 10 conscious resting trained male dogs, plasma growth hormone (GH) was determined at 5-min intervals by radioimmunoassay. For all experiments, the basal GH concentration in plasma was 0.80 ± 0.06 ng mL−1. In each experiment, 1–3 secretory bursts of GH occurred, raising plasma GH 2.4 to 15.3 times basal concentrations (for all 43 bursts, 6.6 ± 0.4 times the basal value). Metabolic clearance rates (MCR) and apparent distribution volumes (V) were determined, using stepwise infusions of canine GH. The MCR (3.99 ± 0.30 mL kg−1 min−1) and V (57.9 ± 5.5 mL kg−1) were used to transform the GH concentration versus time data into GH secretion rates, using a single compartment approach. Basal GH secretion rates for all 28 experiments were 3.12 ± 0.24 ng kg−1 min−1. The secretory bursts yield peak GH secretion rates of 9.4 ± 0.8 times basal secretion and these steep-sloped bursts last 25.1 ± 1.2 min. Six-hour infusions of 0.15 μg kg−1 min−1 of somatostatin (SRIF) abolished all secretory bursts but did not lower basal secretion rates. In five of seven SRIF infusion experiments in which samples were taken after the infusion ceased a secretory burst was seen in the hour following cessation of infusion (in four cases within 10 min). These secretory bursts lasted 23.0 ± 2.9 min and were similar to those seen in control experiments. Infusions of SRIF at 0.05 μg kg−1 min−1 had no effect. These results imply that during basal GH secretion, a surfeit of SRIF impinges on the somatotrophs, as extra SRIF does not further lower basal secretion. However, during secretory bursts, very little SRIF must be present, as exogenous SRIF blocks these bursts. The bursts are similar in duration to overshoots provoked in perifused dispersed rat somatotrophs by removal of an SRIF signal. It seems likely that their cause in vivo is similar. (All values are means ± SEM.)

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