REGULATION OF GROWTH HORMONE SECRETION IN THE OVINE FOETUS

1973 ◽  
Vol 58 (1) ◽  
pp. 89-95 ◽  
Author(s):  
A. L. C. WALLACE ◽  
B. D. STACY ◽  
G. D. THORBURN
Keyword(s):  
Growth Hormone ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
High Rate ◽  
Metabolic Clearance ◽  
Abrupt Decrease ◽  
Gh Secretion ◽  
High Concentrations ◽  
Plasma Gh ◽  
Regulation Of Growth

SUMMARY The rate of removal of immunoreactive, intravenously injected 125I-labelled sheep growth hormone (GH) was used to calculate metabolic clearance rates (MCR) in two foetal lambs at 130 days of gestation and in two 6-day-old lambs. The mean MCR calculated for the foetuses was 2·9 ml/min/kg and for the lambs 3·1 ml/min/kg. The concentration of GH in plasma sampled before injection was determined immunologically and the values were used to calculate production rates. A production rate of 924 ng GH/min was calculated for the foetuses and 85 ng GH/min for the lambs. The effect of sectioning the pituitary stalk was studied in two foetuses; after the operation there was a rapid decrease in the circulating levels of GH. Hypophysectomy in two other foetuses also caused an abrupt decrease in plasma GH concentration. It was concluded from these experiments that the exceptionally high concentrations of GH in the plasma of foetal lambs could not be attributed to impaired removal of the hormone from the circulation. The direct cause of the increased hormone concentrations was a high rate of GH secretion resulting from active stimulation of the foetal pituitary by the hypothalamus.

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.)

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

1995 ◽  
Vol 144 (1) ◽  
pp. 83-90 ◽  
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

Somatostatin tonically inhibits growth hormone secretion in domestic fowl

1986 ◽  
Vol 111 (1) ◽  
pp. 91-97 ◽  
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

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

CHLORPROMAZINE INHIBITS EPISODIC GROWTH HORMONE SECRETION IN THE RAT

1979 ◽  
Vol 91 (3) ◽  
pp. 428-436 ◽  
Author(s):  
Ichiji Wakabayashi ◽  
Megumi Kanda ◽  
Nobuyasu Miki ◽  
Reiko Demura ◽  
Kazuo Shizume
Keyword(s):  
Growth Hormone ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Right Atrial ◽  
Plasma Prolactin ◽  
Medial Basal Hypothalamus ◽  
Conscious Rats ◽  
Gh Secretion ◽  
Episodic Growth ◽  
Plasma Gh

ABSTRACT Effects of chlorpromazine (CPZ) on plasma GH and prolactin levels were observed in conscious rats provided with chronic indwelling right atrial cannulae. The administration of CPZ (200 μg/100 g b.w. iv) suppressed episodic plasma GH burst and resulted in significant elevations of plasma prolactin levels. These were also observed in rats in which two types of hypothalamic deafferentation, i.e. anterior and complete, had been carried out. The data suggest that CPZ acts within the medial basal hypothalamus and inhibits episodic plasma GH secretion. In addition, it is inferred that catecholamines are involved in the generation of episodic plasma GH burst.

Growth hormone secretion patterns in relation to LH and estradiol secretion throughout normal female puberty

1991 ◽  
Vol 124 (2) ◽  
pp. 129-135 ◽  
Author(s):  
Johanna M.B. Wennink ◽  
Henriette A. Delemarre-van de Waal ◽  
Rik Schoemaker ◽  
Gert Blaauw ◽  
Caro van den Braken ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Pulse Amplitude ◽  
Height Velocity ◽  
Normal Female ◽  
Night Time ◽  
Gh Secretion ◽  
Plasma Gh ◽  
Estradiol Levels

Abstract. Pulsatile growth hormone secretion patterns were studied in relation to luteinizing hormone and estradiol release in 33 healthy (pre)pubertal girls. Plasma GH was determined every 10 min, plasma LH and E2 every hour. Night-time GH release was always higher than daytime GH release. During daytime, all GH secretion parameters, except for the basal GH level, increased significantly from the prepubertal stage to stage B4 before (m−) the menarche (p=0.05) and decreased thereafter (p=0.05). During night-time, mean GH level and the fraction of GH in pulses also tended to increase from stage B1 to stage B4m−. The number of high pulses (>8 μg/l) during day and night together tended to increase until stage B4m− and decreased after the menarche (p=0.05). Height velocity did not correlate with the number of high pulses (Kendall τ=0.14, p=0.14). From stage B1 to B4m− high correlations were observed between E2 levels and GH secretion parameters, particularly during the day (τ=0.59-0.71, p≤0.01). The correlations between LH levels and GH secretion were high as well (τ=0.50-0.81, p≤0.01), but equal during day and night. It is concluded that during puberty 1. spontaneous GH release in girls increases 2-3 fold until the menarche and decreases thereafter, primarily as the result of an increasing and decreasing GH pulse amplitude; 2. diurnally increasing estradiol levels correlated with increasing GH secretion.

scholarly journals Intravenous administration of ghrelin stimulates growth hormone secretion in vagotomized patients as well as normal subjects

2004 ◽  
pp. 447-450 ◽  
Author(s):  
R Takeno ◽  
Y Okimura ◽  
G Iguchi ◽  
M Kishimoto ◽  
T Kudo ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Direct Action ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Normal Subjects ◽  
Vagal Nerve ◽  
Gh Secretion ◽  
Afferent Vagal ◽  
Vagal Afferent ◽  
Plasma Gh

OBJECTIVE: Ghrelin is a potent peptide stimulating GH secretion. Besides its direct action on the pituitary, ghrelin has been reported to stimulate GH release via the vagal afferent nerve in rats. To examine the involvement of vagal nerve in ghrelin-induced GH secretion in humans, GH responses to ghrelin were compared between vagotomized patients with gastrectomy and normal subjects. METHODS: Ghrelin (0.2 microg/kg) or GHRH (1 microg/kg) was administered intravenously in vagotomized patients and normal subjects on separate days, and plasma GH responses to the stimuli were examined. RESULTS: Ghrelin caused a significant plasma GH rise in both vagotomized patients and normal subjects. Peak GH levels in vagotomized patients (37.5+/-16.9 ng/ml) were not different from those in normal subjects (29.9+/-23.1 ng/ml). The areas under the curve of GH response to ghrelin did not differ between the two groups. GHRH also increased GH levels, and peak GH levels and areas under the curve after GHRH stimulation were also comparable between vagotomized patients and normal subjects. CONCLUSIONS: In the present study, the involvement of the afferent vagal nerve in ghrelin-induced GH secretion was not confirmed in humans.

Mechanism of impaired growth hormone secretion in patients with Cushing's disease

1992 ◽  
Vol 127 (1) ◽  
pp. 13-17 ◽  
Author(s):  
Hideo Takahashi ◽  
Hiroshi Bando ◽  
Chenyu Zhang ◽  
Ryuichi Yamasaki ◽  
Shiro Saito
Keyword(s):  
Growth Hormone ◽  
Cushing’S Disease ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Cushing's Disease ◽  
Gh Secretion ◽  
Highly Sensitive ◽  
Low Levels ◽  
Plasma Gh ◽  
Observation Period

The function of the growth hormone-releasing hormone (GHRH)-growth hormone (GH) axis in Cushing's disease was studied by monitoring (a) the GH responses to GHRH loading and L-dopa loading, (b) the GHRH response to L-dopa loading, and (c) the daytime profiles of plasma GH concentration. GH release following GHRH and L-dopa was blunted in patients as compared to that in age-matched control subjects. However, GHRH release following L-dopa was similar in patients and controls. The plasma GH levels in four patients measured every 20 min by a highly sensitive immunoradiometric assay for GH showed pulsatile GH secretion at low levels during the observation period. These results indicate that GHRH release from the hypothalamus is preserved in patients with Cushing's disease, and support the hypothesis that glucocorticoid inhibits GH secretion by altering the hypothalamic somatostatin tone.

Oral dexamethasone administration: new pharmacological test for the assessment of growth hormone secretion

1994 ◽  
Vol 131 (6) ◽  
pp. 598-601 ◽  
Author(s):  
Jaime Pineda ◽  
Pedro Martul ◽  
Felipe F Casanueva ◽  
Carlos Dieguez ◽  
Itxaso Rica ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Gh Deficiency ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Prepubertal Children ◽  
Gh Secretion ◽  
Oral Dexamethasone ◽  
Pharmacological Test ◽  
Plasma Gh ◽  
Normal Adults

Pineda J, Martul P, Casanueva FF, Dieguez C, Rica I, Loridan L. Oral dexamethasone administration: new pharmacological test for the assessment of growth hormone secretion. Eur J Endocrinol 1994;131:598–601. ISSN 0804–4643 Acute intravenous (iv) dexamethasone administration has been described recently as a new test for the diagnosis of growth hormone (GH) deficiency. In the present study, a new protocol of dexamethasone administration was evaluated. Twelve normal adults and 18 normal prepubertal children were studied. The dexamethasone iv test was performed in six adults at a dose of 4 mg and 12 children at a dose of 2 mg/m2. Blood samples were collected 15 min before, at time zero and every 15 or 30 min during 5 h, resulting in a total of 16 samples. In the remaining six adults and six children, 8 and 4 mg, respectively, of dexamethasone were administered orally at the subject's home, and blood sampling started 90 min later when they arrived at the hospital. Plasma GH was measured by radioimmunassay. The dexamethasone-induced GH response (mean ± sem, μg/1) to the iv or oral protocol did not differ in either the adults (iv 8.2 ± 2.1; oral 8.0 ± 1.6) or the children (iv 14.9 ± 1.3; oral 13.6 ± 1.8). It is concluded that the simpler protocol of acute oral dexamethasone administration hereby presented can be a safe and suitable test of GH secretion. J Pineda, Sección de Endocrinologia Pediátrica, Hospital de Cruces, 48903 Baracaldo (Vizcaya), Spain

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