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

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

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Somatostatin tonically inhibits growth hormone secretion in domestic fowl

Journal of Endocrinology ◽

10.1677/joe.0.1110091 ◽

1986 ◽

Vol 111 (1) ◽

pp. 91-97 ◽

Cited By ~ 18

Author(s):

S. Harvey ◽

S.-K. Lam ◽

T. R. Hall

Keyword(s):

Growth Hormone ◽

Domestic Fowl ◽

Hormone Secretion ◽

Growth Hormone Secretion ◽

Passive Immunization ◽

Inhibitory Effect ◽

Gh Secretion ◽

Basal Plasma ◽

Plasma Gh

ABSTRACT Passive immunization of immature chickens with sheep somatostatin (SRIF) antiserum promptly increased the basal plasma GH concentration and augmented TRH-induced GH secretion. Although exogenous SRIF had no inhibitory effect on the basal GH concentration in untreated birds or birds pretreated with non-immune sheep serum, it suppressed the stimulatory effect of SRIF immunoneutralization on GH secretion. These results suggest that SRIF is physiologically involved in the control of GH secretion in birds, in which it appears to inhibit GH release tonically. J. Endocr. (1986) 111, 91–97

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Physiological control of growth hormone secretion by thyrotrophin-releasing hormone in the domestic fowl

Journal of Endocrinology ◽

10.1677/joe.0.1050351 ◽

1985 ◽

Vol 105 (3) ◽

pp. 351-355 ◽

Cited By ~ 16

Author(s):

H. Klandorf ◽

S. Harvey ◽

H. M. Fraser

Keyword(s):

Domestic Fowl ◽

Hormone Secretion ◽

Growth Hormone Secretion ◽

Physiological Control ◽

Thyrotrophin Releasing Hormone ◽

Releasing Hormone ◽

Gh Secretion ◽

Normal Sheep Serum ◽

Plasma Gh

ABSTRACT Immature cockerels (4- to 5-weeks old) were passively immunized, with antiserum raised in sheep, against thyrotrophin-releasing hormone (TRH). The administration of TRH antiserum (anti-TRH) at doses of 0·5, 1·0 or 2·0 ml/kg lowered, within 1 h, the basal concentration of plasma GH for at least 24 h. The administration of normal sheep serum had no significant effect on the GH concentration in control birds. Although the GH response to TRH (1·0 or 10·0 μg/kg) was not impaired in birds treated 1 h previously with anti-TRH, prior incubation (at 39 °C for 1 h) of TRH (20 μg/ml) with an equal volume of anti-TRH completely suppressed the stimulatory effect of TRH (10 pg/kg) on GH secretion in vivo. These results suggest that TRH is physiologically involved in the hypothalamic control of GH secretion in the domestic fowl. J. Endocr. (1985) 105, 351–355

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

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y84-030 ◽

1984 ◽

Vol 62 (2) ◽

pp. 199-207 ◽

Cited By ~ 9

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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Obestatin Partially Affects Ghrelin Stimulation of Food Intake and Growth Hormone Secretion in Rodents

Endocrinology ◽

10.1210/en.2006-1231 ◽

2007 ◽

Vol 148 (4) ◽

pp. 1648-1653 ◽

Cited By ~ 125

Author(s):

Philippe Zizzari ◽

Romaine Longchamps ◽

Jacques Epelbaum ◽

Marie Thérèse Bluet-Pajot

Keyword(s):

Food Intake ◽

Hormone Secretion ◽

Growth Hormone Secretion ◽

Male Rats ◽

Pituitary Cells ◽

Gh Secretion ◽

Freely Moving ◽

Stimulation Of

Administration of ghrelin, an endogenous ligand for the GH secretagogue receptor 1a (GHSR 1a), induces potent stimulating effects on GH secretion and food intake. However, more than 7 yr after its discovery, the role of endogenous ghrelin remains elusive. Recently, a second peptide, obestatin, also generated from proteolytic cleavage of preproghrelin has been identified. This peptide inhibits food intake and gastrointestinal motility but does not modify in vitro GH release from pituitary cells. In this study, we have reinvestigated obestatin functions by measuring plasma ghrelin and obestatin levels in a period of spontaneous feeding in ad libitum-fed and 24-h fasted mice. Whereas fasting resulted in elevated ghrelin levels, obestatin levels were significantly reduced. Exogenous obestatin per se did not modify food intake in fasted and fed mice. However, it inhibited ghrelin orexigenic effect that were evident in fed mice only. The effects of obestatin on GH secretion were monitored in superfused pituitary explants and in freely moving rats. Obestatin was only effective in vivo to inhibit ghrelin stimulation of GH levels. Finally, the relationship between octanoylated ghrelin, obestatin, and GH secretions was evaluated by iterative blood sampling every 20 min during 6 h in freely moving adult male rats. The half-life of exogenous obestatin (10 μg iv) in plasma was about 22 min. Plasma obestatin levels exhibited an ultradian pulsatility with a frequency slightly lower than octanoylated ghrelin and GH. Ghrelin and obestatin levels were not strictly correlated. In conclusion, these results show that obestatin, like ghrelin, is secreted in a pulsatile manner and that in some conditions; obestatin can modulate exogenous ghrelin action. It remains to be determined whether obestatin modulates endogenous ghrelin actions.

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Effect of actively immunizing sheep against growth hormone-releasing hormone or somatostatin on spontaneous pulsatile and neostigmine-induced growth hormone secretion

Journal of Endocrinology ◽

10.1677/joe.0.1440083 ◽

1995 ◽

Vol 144 (1) ◽

pp. 83-90 ◽

Cited By ~ 17

Author(s):

E Magnan ◽

L Mazzocchi ◽

M Cataldi ◽

V Guillaume ◽

A Dutour ◽

...

Keyword(s):

Growth Hormone ◽

Body Weight ◽

Hormone Secretion ◽

Growth Hormone Secretion ◽

Physiological Role ◽

Gh Secretion ◽

Igf I ◽

Plasma Gh ◽

Hypophysial Portal

Abstract The physiological role of endogenous circulating GHreleasing hormone (GHRH) and somatostatin (SRIH) on spontaneous pulsatile and neostigmine-induced secretion of GH was investigated in adult rams actively immunized against each neuropeptide. All animals developed antibodies at concentrations sufficient for immunoneutralization of GHRH and SRIH levels in hypophysial portal blood. In the anti GHRH group, plasma GH levels were very low; the amplitude of GH pulses was strikingly reduced, although their number was unchanged. No stimulation of GH release was observed after neostigmine administration. The reduction of GH secretion was associated with a decreased body weight and a significant reduction in plasma IGF-I concentration. In the antiSRIH group, no changes in basal and pulsatile GH secretion or the GH response to neostigmine were observed as compared to controls. Body weight was not significantly altered and plasma IGF-I levels were reduced in these animals. These results suggest that in sheep, circulating SRIH (in the systemic and hypophysial portal vasculature) does not play a significant role in pulsatile and neostigmine-induced secretion of GH. The mechanisms of its influence on body weight and production of IGF-I remain to be determined. Journal of Endocrinology (1995) 144, 83–90

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

Acta Endocrinologica ◽

10.1530/acta.0.0930134 ◽

1980 ◽

Vol 93 (2) ◽

pp. 134-138 ◽

Cited By ~ 4

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.

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

Acta Endocrinologica ◽

10.1530/acta.0.1140465 ◽

1987 ◽

Vol 114 (4) ◽

pp. 465-469 ◽

Cited By ~ 21

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.

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Effect of synthetic thyrotrophin-releasing hormone and its analogues on growth hormone secretion in the domestic fowl (Gallus Domesticus)

Acta Endocrinologica ◽

10.1530/acta.0.0970448 ◽

1981 ◽

Vol 97 (4) ◽

pp. 448-453 ◽

Cited By ~ 19

Author(s):

C. G. Scanes ◽

S. Harvey ◽

B. A. Morgan ◽

M. Hayes

Keyword(s):

Growth Hormone ◽

Domestic Fowl ◽

Hormone Secretion ◽

Growth Hormone Secretion ◽

Gallus Domesticus ◽

Plasma Growth Hormone ◽

Thyrotrophin Releasing Hormone ◽

Releasing Hormone ◽

Gh Secretion ◽

Trh Analogues

Abstract. Variations in plasma growth hormone (GH) concentrations following iv or sc administration of synthetic thyrotrophin-releasing hormone (TRH, Pyr-His-Pro-NH2) have been followed in immature and adult domestic fowl. TRH markedly stimulated GH secretion in newly hatched (1 and 2 day old) chicks and in 6-week-old cockerels but in adult male or female birds of two strains had very little effect, if any. Intravenous injection of 4 TRH analogues (Pyr-His-Mep-NH2, Pyr-Meh-Mep-NH2, Pyr-Meh-Mep-NH and Pyr-Meh-Pro-NH2) were also potent GH secretagogues in 6-week-old birds. The stimulatory effect of TRH or the TRH-analogues on GH secretion was not dose-related.

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Central action of thyrotrophin-releasing hormone on growth hormone secretion in domestic fowl

Journal of Endocrinology ◽

10.1677/joe.0.1260083 ◽

1990 ◽

Vol 126 (1) ◽

pp. 83-88 ◽

Cited By ~ 6

Author(s):

S. Harvey ◽

R. W. Lea ◽

C. Ahene

Keyword(s):

Growth Hormone ◽

Domestic Fowl ◽

Hormone Secretion ◽

Plasma Concentrations ◽

Growth Hormone Secretion ◽

Central Effect ◽

Central Action ◽

Thyrotrophin Releasing Hormone ◽

Gh Secretion ◽

Peripheral Plasma

ABSTRACT Peripheral plasma concentrations of GH in adult chickens were increased, in a dose-related manner, between 5 and 30 min after the intracerebroventricular (i.c.v.) injection of 0·1 or 10 μg TRH. In contrast, i.v. administration of comparable doses of TRH had no significant effect on circulating GH concentrations. [3H]3-methyl-histidine2-TRH ([3H]Me-TRH) was located in the pituitary gland and peripheral plasma within 5 min of its i.c.v. administration, although in amounts that were unlikely to affect directly pituitary function. [3H]Me-TRH rapidly accumulated in the hypothalamus following its i.c.v. administration (but not after i.v. injection), and the central effect of TRH on GH secretion in birds is therefore likely to be induced by effects at hypothalamic sites. Journal of Endocrinology (1990) 126, 83–88

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