Effects of hysterectomy and in-vivo treatment with uterine extracts on plasma concentrations of growth hormone, thyrotrophin and thyroid hormones in rats: a kinetic study

1984 ◽  
Vol 101 (3) ◽  
pp. 243-248 ◽  
Author(s):  
J. Bíró ◽  
P. Eneroth ◽  
E. M. Ritzén
Keyword(s):  
Growth Hormone ◽  
Thyroid Hormones ◽  
Kinetic Study ◽  
Plasma Concentrations ◽  
Adult Rats ◽  
In Vivo Treatment ◽  
Plasma Gh

ABSTRACT Plasma concentrations of GH, TSH, tri-iodothyronine (T3) and thyroxine (T4) were measured in adult rats 2 and 4 weeks after ovariectomy and ovariohysterectomy. Two weeks after ovariohysterectomy, the concentration of GH was significantly higher, but TSH and T3 concentrations were significantly lower than in rats which had been ovariectomized only. Hysterectomy had no effect on plasma GH and TSH concentrations if it was performed 2 weeks after ovariectomy. Plasma T3 had decreased by 2 weeks after ovariectomy but returned to pretreatment levels by 4 weeks. Recovery of the plasma T3 concentration was not observed if ovariectomy was followed by hysterectomy, since a further decrease of plasma T3 occurred. Plasma T4 was not significantly influenced either by ovariectomy or by ovariohysterectomy. Steroid-free uterine extracts given i.p. to ovariohysterectomized rats reduced plasma GH within 24 h of injection. Increases in plasma TSH, T3 and T4 were achieved in ovariohysterectomized rats with injections of uterine extracts (from intact, oestrogen-treated or castrated rats), but the increases were not consistent for the three hormones either as regards time after injection, nor for which particular extracts were effective. It was concluded that the uterus may contain factors which influence the GH storage and secretion and TSH-thyroid regulation in rats. J. Endocr. (1984) 101, 243–248

Mechanism of action of Hexarelin. I. Growth hormone-releasing activity in the rat

1996 ◽  
Vol 135 (4) ◽  
pp. 481-488 ◽  
Author(s):  
Antonio Torsello ◽  
Roberta Grilli ◽  
Marina Luoni ◽  
Margherita Guidi ◽  
Maria Cristina Ghigo ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Mechanism Of Action ◽  
Direct Action ◽  
Male Rats ◽  
Surgical Ablation ◽  
Adult Rats ◽  
Gh Secretion ◽  
Plasma Gh

Torsello A, Grilli R, Luoni M, Guidi M, Ghigo MC, Wehrenberg WB, Deghenghi R, Müller EE, Locatelli V. Mechanism of action of Hexarelin. I. Growth hormone-releasing activity in the rat. Eur J Endocrinol 1996;135:481–8. ISSN 0804–4643 We have reported Hexarelin (HEXA), an analog of growth hormone-releasing peptide 6 (GHRP-6), potently stimulates growth hormone (GH) secretion in infant and adult rats. This study was undertaken to further investigate Hexarelin's mechanisms of action. In 10-day-old pups, treatments with HEXA (80 μg/kg, b.i.d.) for 3–10 days significantly enhanced, in a time-related fashion, the GH response to an acute HEXA challenge. Qualitatively similar effects were elicited in pups passively immunized against growth hormone-releasing hormone (GHRH) from birth. In adult male rats, a 5-day pretreatment with HEXA (150 μg/kg, b.i.d.) did not enhance the effect of the acute challenge, and the same pattern was present after a 5-day pretreatment in male rats with surgical ablation of the mediobasal hypothalamus (MBH-ablated rats). In addition, in adult sham-operated rats, Hexarelin (300 μg/kg, iv) induced a GH response greater (p < 0.05) than that induced by GHRH (2 μg/kg, iv). However, in MBH-ablated rats 7 days after surgery, GHRH was significantly (p < 0.05) more effective than HEXA, and 30 days after surgery HEXA and GHRH evoked similar rises of plasma GH. Finally, the in vitro Hexarelin (10−6 mol/l) effect was transient while GHRH (10−8 mol/l) induced a longer lasting and greater GH release. Three different mechanisms, not mutually exclusive, are postulated for Hexarelin stimulation of GH secretion in vivo: a direct action on the pituitary, though of minor relevance; an indirect action that involves release of GHRH, of relevance only in adult rats; and an action through the release of a still unknown hypothalamic "factor", which in infant and adult rats elicits GH release acting sinergistically with GHRH. Antonio Torsello, Department of Pharmacology, via Vanvitelli 32, 20129 Milano, Italy

Effects of hysterectomy and uterine extracts on growth hormone, somatomedin, prolactin, thyrotrophin and thyroid hormones in adult rats

1983 ◽  
Vol 103 (2) ◽  
pp. 172-179 ◽  
Author(s):  
J. Bíró ◽  
E. M. Ritzén ◽  
K. Hall ◽  
P. Eneroth
Keyword(s):  
Growth Hormone ◽  
Anterior Pituitary ◽  
Plasma Concentrations ◽  
Endocrine System ◽  
Thyroid Stimulating Hormone ◽  
The Body ◽  
Biologically Active ◽  
Female Rats ◽  
Adult Rats ◽  
Plasma Gh

Abstract. Plasma concentrations and anterior pituitary content of growth hormone (rGH), thyroid stimulating hormone (rTSH), and rat prolactin (rPrl) as well as the plasma concentrations of triiodothyronine (T3), thyroxine (T4) and somatomedin A (SM-A) have been determined in intact, castrated or hysterectomized adult rats with and without treatment with steroid-free, crude uterine extracts. Hysterectomy caused a significant increase in the plasma GH but decrease in the plasma TSH concentrations. Injection of crude, steroid-free uterine extracts for 14 days had the following effects: decreased plasma GH concentration of intact rat and anterior pituitary GH content of both intact and castrated animals; increased plasma TSH and T3 concentrations above the ovariectomized control; decreased pituitary content of prolactin in castrated rats. The plasma levels of immunoreactive somatomedins A were negatively correlated to the plasma GH concentrations but positively correlated to the body weight. It was concluded that the uterus is not only a target for different endocrine influences but contains biologically active, non-steroidal substances which have a complex effect on the endocrine system of adult, female rats.

The effect of restricted feeding on growth hormone (GH) secretory patterns in genetically lean and fat wether lambs

2000 ◽  
Vol 70 (3) ◽  
pp. 425-433 ◽  
Author(s):  
S. M. Francis ◽  
R. P. Littlejohn ◽  
S. K. Stuart ◽  
B. A. Veenvliet ◽  
J. M. Suttie
Keyword(s):  
Growth Hormone ◽  
Treatment Group ◽  
Developmental Change ◽  
Plasma Concentrations ◽  
Live Weight ◽  
Carcass Composition ◽  
Restricted Feeding ◽  
Ad Libitum ◽  
Plasma Gh ◽  
And Control

AbstractThe aim of this work was to determine whether developmental changes in growth hormone (GH) secretory patterns and carcass composition were influenced by nutrition and genotype in sheep. Four-month-old wether lambs from lean (low backfat), fat (high backfat) and control selection lines were nutritionally restricted to maintain a 28 kg live weight or given food ad libitum for 24 weeks. Plasma concentrations of GH and insulin-like growth factor 1 (IGF-1) were measured at predetermined times and carcass composition of the animals determined at the end of the trial.From week 3 on, restrictions in dry matter (DM) intake were observed as the ad libitum treatment group had a significantly greater intake than the restricted treatment group (7·70 v. 5·80 kg DM per week, s.e.d. = 0·81). Differences in live weight between the feeding treatments were significant (P < 0·05) at week 9. The restricted feeding regime was associated with significant reductions in plasma levels of IGF-1 but had no effect (P > 0·05) on carcass weight-adjusted carcass fat proportion at the close of the trial. The effect of food restriction on GH secretory patterns was variable. Although there was initially a suppression in mean plasma GH, there was subsequently significantly higher mean plasma GH in the restricted feeding treatment. Periodogram analysis indicated that both the absolute levels of GH and the GH secretory pattern were altered by restricted feeding. In all animals, mean and basal GH concentrations, as well as the frequency and amplitude of pulses, declined from February to March and then increased from May to July (P < 0·001).DM intake and live weight did not differ (P > 0·05) between genotypes, however the fat genotype had greater carcass fatness than lean or control genotypes (P < 0·01). There were no consistent differences between genotypes in plasma IGF-1 concentrations. In the ad libitum treatment, the lean and control genotypes had higher plasma GH levels than the f at genotype but the pattern of GH release did not vary. Under restricted feeding, both the pattern and the level of plasma GH varied between genotypes.It is concluded that the developmental change in GH secretory patterns is affected by nutrition but not in a consistent manner. Although restricted feeding resulted in higher mean plasma GH concentrations later in the trial, this did not result in a change in carcass composition. The biological cues which lead to increased fat deposition in older lambs need further study but plasma GH levels may not he an important mechanism in this process.

RELATIONSHIP BETWEEN LAMB BIRTH WEIGHTS AND FETAL PLASMA GROWTH HORMONE AND INSULIN CONCENTRATIONS

1986 ◽  
Vol 66 (4) ◽  
pp. 995-1001
Author(s):  
G. J. MEARS
Keyword(s):  
Growth Hormone ◽  
Fetal Growth ◽  
Plasma Insulin ◽  
Plasma Concentrations ◽  
Maternal Plasma ◽  
Metabolic Clearance ◽  
Plasma Growth Hormone ◽  
Fetal Plasma ◽  
Plasma Gh ◽  
Ovine Fetal

Plasma concentrations of growth hormone (GH) and insulin were monitored in 11 chronically cannulated ovine fetuses and their mothers during the last month of gestation to obtain information on the role that these hormones have in determining fetal growth rate. Maternal plasma GH and insulin concentrations were independent of stage of gestation and lamb birth weights. Fetal plasma insulin concentrations were episodic in nature, independent of stage of gestation, and tended to be higher in fetuses that were heavier at birth. Fetal plasma GH concentrations were only slightly episodic in nature, were tenfold higher than maternal levels at 116–124 d gestation and increased by approximately another 25% prior to parturition. Fetal plasma GH concentrations were negtively correlated with lamb birth weights. In twin preparations, fetal plasma GH concentrations were significantly lower in the twin that was heaviest at birth. The lower GH concentrations found in faster growing fetuses are suggestive of a more rapid metabolic clearance of GH by the tissues of these animals. The results indicate that circulating fetal GH and, possibly, insulin are involved in determining the rate of ovine-fetal growth. Key words: Ovine birth weights, fetal GH, fetal insulin, fetal growth

Manipulation of protein and fat accretion in growing cattle

1991 ◽  
Vol 1991 ◽  
pp. 18-18
Author(s):  
J.M. Dawson ◽  
D.E. Beever ◽  
P.J. Buttery ◽  
M. Gill
Keyword(s):  
Growth Hormone ◽  
Muscle Protein ◽  
Adrenergic Agonists ◽  
Plasma Growth Hormone ◽  
Direct Stimulation ◽  
Hormone Administration ◽  
Young Cattle ◽  
Plasma Gh

ß-adrenergic agonists are powerful repartitioning agents, increasing muscle protein accretion and reducing fat deposition in a variety of species. Their exact mode of action is not fully understood but some of their effects are similar to those elicited by exogenous growth hormone administration. Whilst there are few reports of plasma growth hormone (GH) concentrations being elevated in animals treated with ß-agonists, several in vitro studies have clearly demonstrated a direct stimulation of GH release from perifused or cultured pituitary or adenohypophyseal cells on administration of these agents. More recently, a brief, rapid rise in plasma GH has been demonstrated in rats infused intra-atrially with isoproterenol and this was sustained when the animals were pre-treated with somatotropin release inhibitory factor (somatostatin; SRIF) antiserum. This raises the possibility that ß-adrenergic agonists do stimulate GH release in vivo but that this response is rapidly counteracted by SRIF release.The aim of this work was to attempt to enhance the repartitioning effect of ß-adrenergic agonists by immunizing young cattle against SRIF whilst administering cimaterol.

TRH and GRF stimulate release of growth hormone through different mechanisms

1986 ◽  
Vol 250 (5) ◽  
pp. E512-E517
Author(s):  
M. Szabo
Keyword(s):  
Growth Hormone ◽  
Response Curves ◽  
Calcium Dependent ◽  
System A ◽  
Effective Doses ◽  
Primary Monolayer ◽  
Plasma Gh ◽  
Primary Monolayer Cultures

Thyrotropin-releasing hormone (TRH) is an effective stimulator of growth hormone (GH) release from cultured adenohypophysial cells of chronically hypothyroid rats in vitro. The present study explored the question of cAMP and calcium mediation of the GH-stimulatory effect of TRH in this system. A maximally stimulatory concentration of TRH was added together with various concentrations of human GH-releasing factor 40 (hGRF-40) whose action is cAMP mediated, or of dibutyryl cAMP (DBcAMP), to primary monolayer cultures of adenohypophysial cells from thyroidectomized rats. The GH responses to the combined addition of TRH with all doses of GRF or DBcAMP were fully additive, causing parallel elevations of the dose-response curves. Whereas the GH response to maximally effective concentrations of hGRF-40 and DBcAMP, added together, was not greater than that to either secretagogue alone, the inclusion of TRH increased the response to a new Emax. The calcium inhibitors, verapamil, EGTA, and CoCl2, markedly suppressed basal GH release and virtually completely blocked the GH response to TRH, suggesting calcium mediation. In chronically hypothyroid, urethan-anesthetized rats, the in vivo effect of the combined administration of maximally effective doses of TRH and GRF on plasma GH levels was also additive. These findings indicate that TRH stimulates GH release in adenohypophysial cells of hypothyroid rats by a cAMP-independent, calcium-dependent mechanism.

Uridine triphosphate and RNA synthesis during diabetes-induced renal growth

1980 ◽  
Vol 238 (4) ◽  
pp. E349-E357
Author(s):  
P. Cortes ◽  
N. W. Levin ◽  
F. Dumler ◽  
A. H. Rubenstein ◽  
C. P. Verghese ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Rna Synthesis ◽  
Insulin Infusion ◽  
Renal Cortex ◽  
Plasma Concentrations ◽  
Synthesis Rate ◽  
Renal Growth ◽  
Rna Content ◽  
And Control

UTP, CTP, and RNA synthesis were studied in the renal cortex of diabetic and control rats in vivo. The incorporation of UTP into RNA (nmol/h DNA) was used as estimate of RNA synthesis rate. Two to three days after streptozotocin injection, UTP and CTP ppol size and orotate incorporation into UTP and RNA were greater in diabetic animals than in controls. In addition, RNA content and RNA synthesis rate were increased. These changes were corrected by insulin infusion. In diabetic animals, additional increases in UTP pool, RNA content, and RNA synthesis rate followed contralateral nephrectomy. This increase in RNA content was greater than in uninephrectomized controls. The changes in the diabetic renal cortex were not accompanied by increased plasma concentrations of growth hormone. The increase in RNA content in the diabetic renal cortex is probably due to increased RNA synthesis. Increased synthesis of pyrimidines and expansion of the UTP pool may make this substrate more readily available for the synthesis of UDP sugars and may facilitate the synthesis of basement membrane in diabetes.

Progesterone-controlled growth hormone overproduction and naturally occurring canine diabetes and acromegaly

1983 ◽  
Vol 104 (2) ◽  
pp. 167-176 ◽  
Author(s):  
J. Eugen Eigenmann ◽  
Rina Y. Eigenmann ◽  
Ad Rijnberk ◽  
Ingrid van der Gaag ◽  
Jürgen Zapf ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Glucose Tolerance ◽  
Glucose Intolerance ◽  
Plasma Concentrations ◽  
Spontaneous Diabetes ◽  
Tolerance Test ◽  
Glucose Levels ◽  
Tissue Changes ◽  
Soft Tissue Changes ◽  
Plasma Gh

Abstract. Female pet dogs exhibiting either glucose intolerance alone or glucose intolerance and acromegaly were investigated. Some dogs developed the disorder(s) during dioestrus and some animals developed the disorder(s) after they were given medroxyprogesterone acetate (MPA). Elevated fasting plasma glucose levels (12.3 ± 1.9 mm, mean ± sem) were accompanied by fasting hyperinsulinaemia (144 ± 21 μU/ml, mean ± sem) and drastic elevation of plasma growth hormone (GH) levels (112.6 ± 45 ng/ml, mean ± sem). An iv glucose tolerance test (IVGTT) performed on all dogs revealed non-suppressibility of GH levels and glucose intolerance. Plasma concentrations of glucose, insulin and GH during IVGTT in affected dogs differed significantly from the concentrations measured in normal dogs during the same test. MPA withdrawal and/or ovariohysterectomy (OVx-HYx) in affected animals was followed by reversal of GH levels to normal and improved glucose tolerance. Acromegaly associated soft tissue changes were also reversible after MPA withdrawal and/or OVx-HYx when GH levels had dropped. In 5 dogs which had developed diabetes during dioestrus and in which a spontaneous decrease in plasma progesterone occurred during the investigation a concomittant decrease in GH levels was observed. Plasma GH measured at different stages of pregnancy in 45 dogs was found to be elevated in one animal only. The results show that the development of spontaneous diabetes/acromegaly occurring in some female dogs is related to progestagen (progesterone/MPA) exposure and that reversal of the signs is achieved by progesterone/MPA withdrawal. The results suggest that diabetes/acromegaly in the dogs studied was caused by progesterone/MPA-evoked GH elevation. Finally, the findings also suggest that the GH axis normally not appreciably responsive to progestagen exposure in some dogs becomes and/or is paradoxically controlled by physiologic levels of endogenous progesterone or low doses of MPA.

On the role of the peptide galanin in regulation of growth hormone secretion

1991 ◽  
Vol 125 (5) ◽  
pp. 518-525 ◽  
Author(s):  
Anna-Lena Hulting ◽  
Björn Meister ◽  
Lena Carlsson ◽  
Agneta Hilding ◽  
Olle Isaksson
Keyword(s):  
Growth Hormone ◽  
Anterior Pituitary ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Pituitary Cells ◽  
Anterior Pituitary Cells ◽  
Human Anterior Pituitary ◽  
Plasma Gh

Abstract. The effects of the peptide galanin on growth hormone secretion were studied in vitro using cultured rat and human anterior pituitary cells, and in vivo by iv administration of galanin in both rats and humans. Galanin in concentrations from 10 nmol/l to 1 μmol/l did not alter basal GH release, but slightly inhibited GHRH-stimulated GH release from cultured rat anterior pituitary cells. Galanin (1 μmol/l) did not significantly change basal or GHRH-stimulated GH secretion from cultured human anterior pituitary cells. In contrast, iv injection of 1 μg (300 pmol) galanin to rats induced an increase in plasma GH that was reproducible at repetitive injections. The galanin-induced GH release in rats was of a lower magnitude than the increase in plasma GH after iv injections of GHRH, and was seen with a 5-15 min delay in comparison to iv administered GHRH. In man, iv infusions of galanin (40 pmol ·kg−1 · min−1 · (40 min)) also caused a significant increase in plasma GH, but it occurred 25-30 min after the beginning of the infusion. These results suggest an indirect action of galanin on GH release in both rats and humans, i.e. galanin does not directly affect the somatotropes. In agreement with a central action, no binding sites for galanin could be demonstrated in the rat anterior pituitary by autoradiography. Since galanin did not affect somatostatin release from fragments of rat mediobasal hypothalamus, the stimulatory effects of galanin on GH release are most likely mediated via a stimulatory effect on GHRH neurons.

Effect of growth hormone on acute glucagon and insulin release.

1979 ◽  
Vol 237 (2) ◽  
pp. E107 ◽  
Author(s):  
A Sirek ◽  
M Vranic ◽  
O V Sirek ◽  
M Vigas ◽  
Z Policova
Keyword(s):  
Growth Hormone ◽  
Peak Plasma ◽  
Plasma Concentrations ◽  
Immunoreactive Insulin ◽  
Sudden Rise ◽  
Physiological Dose ◽  
Diabetic Dogs ◽  
Pancreatectomized Dogs ◽  
Glucagon And Insulin

The aim was to clarify whether or not sudden spike concentrations of plasma growth hormone (GH) can affect the endocrine pancreas in vivo. The peaking of GH was reproduced by an injection (10 mg/kg iv) of bovine GH to anesthetized normal, pancreatectomized, and alloxan-diabetic dogs. In portal but not in peripheral blood, immunoreactive plasma glucagon (IRG), glucagon-like activity (GLI), and immunoreactive insulin (IRI), were significantly elevated within 10 min in normal and alloxan-diabetic dogs. In pancreatectomized dogs, GH did not affect either IRG or GLI. When a physiological dose of GH (6 microgram/kg) calculated to produce ambient peak plasma concentrations of 40 ng/ml was given to four conscious, normal dogs with indwelling portal catheters, a rise of IRG from 108 +/- 19 to 170 +/- 17 pg/ml and of IRI from 20 +/- 12 to 67 +/- 19 muU/ml (mean +/- SE) occurred within 2 min. GLI was not affected. Thus a sudden rise in GH concentration can stimulate the release of a) GLI in the presence but not in the absence of the pancreas, and b) pancreatic IRG and IRI but not extrapancreatic IRG.

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