Single Injection Of Growth Hormone Research Articles

Early Life Nociception is Influenced by Peripheral Growth Hormone Signaling.

A number of cellular systems work in concert to modulate nociceptive processing in the periphery, but the mechanisms that regulate neonatal nociception may be distinct compared with adults. Our previous work indicated a relationship between neonatal hypersensitivity and growth hormone (GH) signaling. Here, we explored the peripheral mechanisms by which GH modulated neonatal nociception under normal and injury conditions (incision) in male and female mice. We found that GH receptor (GHr) signaling in primary afferents maintains a tonic inhibition of peripheral hypersensitivity. After injury, a macrophage dependent displacement of injury-site GH was found to modulate neuronal transcription at least in part via serum response factor (SRF) regulation. A single GH injection into the injured hindpaw muscle effectively restored available GH signaling to neurons and prevented acute pain-like behaviors, primary afferent sensitization, and neuronal gene expression changes. GH treatment also inhibited long-term somatosensory changes observed after repeated peripheral insult. Results may indicate a novel mechanism of neonatal nociception.SIGNIFICANCE STATEMENT Although it is noted that mechanisms of pain development in early life are unique compared with adults, little research focuses on neonatal-specific peripheral mechanisms of nociception. This gap is evident in the lack of specialized care for infants following an injury including surgeries. This report evaluates how distinct cellular systems in the periphery including the endocrine, immune and nervous systems work together to modulate neonatal-specific nociception. We uncovered a novel mechanism by which muscle injury induces a macrophage-dependent sequestration of peripheral growth hormone (GH) that effectively removes its normal tonic inhibition of neonatal nociceptors to promote acute pain-like behaviors. Results indicate a possible new strategy for treatment of neonatal postsurgical pain.

Growth hormone increases regulator of calcineurin 1-4 (Rcan1-4) mRNA through c-JUN in rat liver.

Growth hormone (GH) activates multiple signal transduction pathways. To investigate these pathways, we identified novel genes whose transcription was induced by GH in the liver of hypophysectomized (HPX) rats using the suppression subtractive hybridization technique. We found that regulator of calcineurin 1 (Rcan1) mRNA was upregulated by GH administration. RCAN1 regulates the activity of calcineurin, a Ca/calmodulin-dependent phosphatase. Rcan1 encodes two major transcripts, Rcan1-1 and Rcan1-4, resulting from differential promoter use and first exon choice. We found that a single injection of GH increased the levels of Rcan1-4 mRNA and RCAN1-4 protein transiently, but did not increase Rcan1-1 mRNA in HPX rat liver. Then the molecular mechanism of GH to induce Rcan1-4 transcription was examined in rat hepatoma H4IIE cells. Experiments using inhibitors suggested that c-JUN N-terminal kinase was required for the induction of Rcan1-4 mRNA by GH. GH increased the levels of phosphorylated c-JUN protein and c-Jun mRNA in HPX rat liver. The luciferase and electrophoretic mobility shift assays showed that c-JUN upregulated Rcan1-4 mRNA by binding to the cAMP-responsive element in the upstream of Rcan1 exon 4. These results indicate that GH activates c-JUN to affect the activity of calcineurin by the induction of Rcan1-4 in rat liver.

Regulation of growth hormone (GH) receptor (GHR1 and GHR2) mRNA level by GH and metabolic hormones in primary cultured tilapia hepatocytes

Growth hormone (GH) regulates essential physiological functions in teleost fishes, including growth, metabolism, and osmoregulation. Recent studies have identified two clades of putative receptors for GH (GHR1 clade and GHR2 clade) in fishes, both of which are highly expressed in the liver. Moreover, the liver is an important target for the anabolic effects of GH via endocrine IGFs, and liver sensitivity to GH is modulated by metabolic hormones. We investigated the effects of GH, insulin, glucagon, cortisol and triiodothyronine on GHR1 and GHR2 mRNA levels in primary cultured tilapia hepatocytes. Physiological concentrations of GH strongly stimulated GHR2 mRNA level (0.5–50×10−9M), but did not affect GHR1 mRNA level. Insulin suppressed stimulation of GHR2 mRNA level by GH (10−8–10−6M). Insulin increased basal GHR1 mRNA level (10−8–10−6M). Cortisol increased basal GHR2 mRNA level (10−7–10−6M), but did not consistently affect GH-stimulated GHR2 mRNA level. Cortisol increased basal GHR1 mRNA level (10−9–10−6M). Glucagon suppressed GH-stimulated GHR2 mRNA level and increased basal GHR1 mRNA level at a supraphysiological concentration (10−6M). A single injection of GH (5μg/g) increased liver GHR2 mRNA level, and insulin injection (5μg/g) decreased both basal and GH-stimulated GHR2 mRNA levels after 6h. In contrast, insulin and GH injection had little effect on liver GHR1 mRNA level. This study shows that GHR1 and GHR2 gene expression are differentially regulated by physiological levels of GH and insulin in tilapia primary hepatocytes.

Whole genome microarray analysis of growth hormone-induced gene expression in bone: T-box3, a novel transcription factor, regulates osteoblast proliferation

Growth hormone (GH) is important in the development and maintenance of bone; however, the IGF-dependent and -independent molecular pathways involved remain to be established. We used microarray analysis to evaluate GH signaling pathways in 4-wk-old GH-deficient mice following a single injection of GH (4 mg/kg body wt) or PBS (n = 6/group) at 6 or 24 h after treatment. Six thousand one hundred sixty genes were differentially expressed at P </= 0.05, and 17% of these genes were identified at both time points. Several of the genes differentially expressed were expressed sequence tags, and the remaining genes fell into 49 Gene Ontology categories. For subsequent studies, we focused on T-box (Tbx)3, a novel transcription factor, which increased more than twofold at both time points. Real-time RT-PCR analysis determined that pretreatment with IGF-binding protein-4 did not block GH-induced Tbx3 expression in vitro. Pretreatment with TNF-alpha blocked GH-induced Tbx3 expression. Tbx3 expression increased during osteoblast differentiation and following BMP-7 and Wnt3a treatment (P </= 0.05). Blocking Tbx3 expression by small interfering RNA decreased cell number and [(3)H]Thymidine incorporation (P < 0.01). In conclusion, 1) GH caused acute changes in several novel genes, suggesting that many GH-induced signaling pathways and target genes remain to be discovered; 2) because Tbx3 expression is regulated in osteoblasts and blockage of Tbx3 expression decreased cell number and DNA synthesis, we propose that Tbx3 is an important determinant of osteoblast cell number.

Hypothalamic STAT Proteins: Regulation of Somatostatin Neurones by Growth Hormone Via STAT5b

Signal transducers and activators of transcription (STATs) are a family of transcription factors linked to class I cytokine receptors. In the present study, we investigated whether their distribution in the hypothalamus reflects the feedback regulation by growth hormone and what role they might play in the functioning of target neurones. We demonstrate that each of the seven known STATs has a distinct distribution in the hypothalamus. Notably, the STAT5 proteins, that are important in growth hormone (GH) and prolactin signalling in peripheral tissues, were expressed in somatostatin neurones of the periventricular nucleus and dopamine neurones of the arcuate nucleus. Because somatostatin neurones are regulated by feedback from circulating GH, we investigated the importance of STAT5 in these neurones. We demonstrate that STAT5b protein expression, similar to somatostatin mRNA, is sexually dimorphic in the periventricular nucleus of rats and mice. Furthermore, chronic infusion of male dwarf rats with GH increased the expression of STAT5b, while a single injection of GH into similar rats induced the phosphorylation of STAT5 proteins. The cellular abundance of somatostatin mRNA in STAT5b-deficient mice was significantly reduced in the periventricular nucleus, effectively reducing the sexually dimorphic expression. These results are consistent with the hypothesis that STAT5 proteins are involved in the feedback regulation of somatostatin neurones by GH, and that these neurones may respond to patterned GH secretion to reinforce sexual dimorphism in the GH axis.

Growth hormone increases IGF-I, collagen I and collagen III gene expression in dwarf rat skeletal muscle

The effect of short-term treatment with biosynthetic growth hormone (GH) of male dwarf rats was studied in EDL and soleus muscles. In situ hybridisation revealed that in the untreated dwarf rat collagen I, collagen III and insulin-like growth factor-I (IGF-I) mRNA is mainly expressed by fibroblasts between the muscle fibre areas. Quantitative image analysis showed that, 8 h after a single GH injection, the level of mRNA for all three genes increased compared to the untreated dwarf animal. IGF-I mRNA levels were similar in normals and untreated dwarf rats but significantly increased 8 h after a single GH injection in EDL ( P < 0.01) and soleus ( P < 0.001). In untreated dwarf rats, collagen I and III gene expression was significantly less than in normal animals ( P < 0.001). Collagen III gene expression also increased significantly 8 h after a single GH injection, in both muscles ( P < 0.01). Collagen I gene expression showed significant increases 8 and 24 h after GH treatment in EDL ( P < 0.01), although the increases seen in soleus did not reach significance. The effects of multiple GH injections (one, two or four) did not appear to be additive. The results of the time course studies are consistent with an intermediary role for IGF-I in the production of collagen in muscle.

Studies on the effects of growth hormone administration in vivo on the rates of glucose transport and utilization in rat skeletal muscle.

The effects of growth hormone (GH) administration to rats in vivo on the sensitivity of the rate of glucose utilization to insulin were studied in soleus muscles isolated from these rats. A single injection of GH did not increase the rate of glucose transport within 1-2 h. However, 12 h after, the rate of glucose transport was increased at 10 mU insulin l-1 and was accompanied by a similar increase in the rate of lactate formation but no change in the rate of glycogen synthesis. Prolonged treatment with GH decreased the rate of glucose transport and glycogen synthesis and increased the content of glucose 6-phosphate at physiological levels of insulin but did not affect the rate of lactate formation. These results suggest that: (a) GH does not increase the rate of glucose transport acutely; however, after several hours, the sensitivity of glucose transport and glycolysis to insulin are increased; (b) prolonged elevations of the level of GH in plasma decrease the sensitivity of the rate of glucose transport and glycogen synthesis to insulin. However, redirection of glucose residues away from the pathway of glycogen synthesis towards that of glycolysis and a possible increase in the rate of glycogenolysis maintain a normal rate of lactate formation, although the rate of glucose transport is decreased.

Acute down-regulation of the somatogenic receptors in rat liver by a single injection of growth hormone.

Prolonged continuous administration of GH induces somatogenic receptors in rat liver. However, because GH secretion is pulsatile and the effect of acute changes in serum GH concentrations on liver GH receptors is unknown, we measured total (MgCl2-treated homogenates) and free (water-treated homogenates) GH-binding sites in the livers of hypophysectomized (hypox) rats killed between 1 and 24 h after a single sc injection of rat GH (100 micrograms/100 g BW; n = 29). Control hypox rats (n = 10) were studied immediately or 3 h after injection of vehicle. GH injection caused profound decreases in both total and free liver GH receptors, but these changes followed different kinetic patterns. Free receptors declined rapidly (to 17% of control), reaching a nadir at the same time (1 h) as the maximal GH concentration in serum. These free receptors then increased, returning to normal 12 h after GH injection. In contrast, total GH receptors were slightly increased at 1 h, decreased to their minimal value at 6 h (53% of control), and returned to normal at 12 h. Serum immunoreactive somatomedin-C/insulin-like growth factor I concentrations peaked 12 h after GH injection. Total and free liver GH receptors were quantitated in hypox rats that had been injected 3 h previously with doses of rat GH from 2.5-500 micrograms/100 g BW or with vehicle. Both total and free binding sites decreased in a dose-dependent manner; the maximal responses were 40% and 90% below control values, respectively. Half-maximal reductions in GH binding were achieved when 10 micrograms GH/100 g BW were given. These data suggest that a surge of GH in serum leads to a time- and dose-dependent down-regulation of the liver somatogenic binding sites and are consistent with ligand-induced internalization and degradation of the receptor.

Evidence of Facilitory Effect of Growth Hormone on Tissue Vitamin A Uptake in Rats

The proposed study was designed to investigate the effect of growth hormone (GH) on liver vitamin A release and uptake at the tissue level. Labeled vitamin A (retinol) was injected in hypophysectomized (hypox) rats, and plasma radioactivity was monitored at intervals for up to 6 hours and at 24 hours following injection. Controls (intact sham-operated) received similar treatment. The results showed that the radioactivity reached its maximum levels in both groups between the third and fourth hours following injection and declined thereafter at different rates in each group. At 24 hours following injection, plasma radioactivity in the intact rats was less than 10% of its maximum levels while in the hypox rats for the same time period it remained at 80--90% of its maximum levels. A single injection of GH at the third hour after injection in the hypox rats decreased significantly (P less than 0.01) plasma radioactivity while radioactivity in the testes and kidneys and in urine collected for the 24 hours increased significantly (P less than 0.01). Hypophysectomy had no effect of vitamin A absorption and liver vitamin A release to the blood. Also, hypophysectomy had no significant effect on plasma and tissue retinol-binding protein levels and its binding capacity to retinol. It is concluded that a facilitory effect of GH at the tissue level may be an important factor in vitamin A metabolism.

Exogenous and endogenous insulin sensitivity following a single growth hormone injection.

Exogenous and endogenous insulin sensitivity following a single growth hormone injection.

Serotonin and the plasma amino acid reduction caused by a single injection of growth hormone.

An acute reduction in the concentration of plasma free amino acids was observed in normal, hypophysectomized, pancreatectomized, and doubly operated (Houssay) dogs following a single injection of bovine growth hormone (NIH, lots B8, B12, and B13, 1–5 mg/kg). The reduction obtained with administered growth hormone in diabetic animals was abolished by dihydroergotamine (2 mg) or 2-brom-d-lysergic acid diethylamide (BOL-148, 1 mg). Pharmacological blockade of the adrenergic and serotonergic systems partially counteracted the growth hormone effect in normal and hypophysectomized dogs; complete suppression was achieved only in combination with puromycin (200 mg). These results indicate that the reduction in the concentration of plasma free amino acids following a single injection of growth hormone has at least two components. It is suggested that one is protein anabolic in nature and the other involves hepatic gluconeogenesis caused chiefly by serotonin.

Effects of growth hormone on the lipolytic response of adipose tissue to theophylline.

Adipose tissue from hypophysectomized rats has a reduced capacity to carry on lipolysis in response to theophylline and other lipolytic agents. Three hr after a single injection of growth hormone (100 μg), FFA and glycerol production in response to theophylline are increased, but basal lipolysis is unchanged. Preincubation of adipose tissue for 3 hr in the presence of 0.01–1.0 μg/ml of growth hormone significantly increased the lipolytic response to theophylline, again without affecting the basal rate of lipolysis. This action of growth hormone has a lag period of more than 1 hr, is blocked by insulin and augmented by dexamethasone, which has a similar, but less consistent effect. Actinomycin failed to block this response to growth hormone and cycloheximide significantly enhanced it. These data are thought to illustrate an effect of growth hormone on the level of 3′,5′-cyclic AMP in adipose tissue, and suggest a biochemical explanation for the “permissive” effect of growth hormone on lipolysis. (Endocrinology81: 1027, 1968)

The effect of dihydroergotamine on plasma free fatty acid concentrations in hypophysectomized dogs following a single injection of growth hormone

Administration of the adrenergic blocking agent dihydroergotamine (DHE) modified the response to a single intravenous injection of bovine GH, in that the initial reduction in the concentration of plasma FFA was abolished in normal and hypophysectomized dogs, and replaced by an abrupt and steep rise especially in hypophysectomized animals. The latter was prevented by treating animals with puromycin. Although the mechanism by which DHE augments the lipolytic effect of GH is not clear, the results show for the first timein vivo that GH-induced lipolysis is a function of protein synthesis and is not the consequence of a direct effect of the hormone on cyclic AMP.

Plasma free fatty acid concentrations in Houssay dogs following a single injection of growth hormone.

A 40% reduction in the concentration of plasma free fatty acids (FFA) was observed within 30 min after an intravenous injection of bovine growth hormone (GH) into depancreatized and Houssay dogs, but in normal animals it was only 20%. It is concluded that GH can produce an acute reduction in the concentration of plasma FFA in the complete absence of the action of insulin. (Endocrinology 81: 395, 1967)

Plasma free fatty acid and glucose concentrations in Houssay dogs

Results of two types of metabolic studies are reported in depancreatized-hypophysectomized dogs maintained without hormonal replacement therapy. The response to a glucose load indicated the presence of severe diabetes, although the animals were not ketonuric and fasting plasma sugars fluctuated around 200 mg %. The response to a single growth hormone injection was that of an acute reduction of the concentration of plasma FFA. Since this occurred in the complete absence of the action of insulin, mechanisms other than insulin-dependent esterification were involved.

Growth hormone-induced diabetes and high levels of serum insulin in dogs.

Single injection of growth hormone (3 mg. per kilogram of body) in fasting dogs did not appreciably alter serum insulin and glucose concentrations within five hours. However, serum free fatty acids (FFA) decreased initially, then rose to two- and fourfold the initial at five and twenty-four hours. Following intravenous injection of glucose (1 gm. per kilogram of body) in the control period, serum insulin rose fourfold in 15 min. then regressed exponentially to the initial. Glucose/insulin remained unchanged during the two-hour test period, despite great alterations in the concentrations of glucose and insulin. Serum FFA decreased, then returned to or above the initial at one to two hours. Single injection of growth hormone did not alter these responses to the infusion of glucose. During the daily administration of 2 mg. of growth hormone per kilogram of body per day: (1) Mean serum insulin concentrations, in the postabsorptive periods, increased to two-, six- and eightfold the control value after one, two and four days, respectively, in six dogs, and thereafter the values remained high during seven to eleven days of observation in four dogs, while two developed resistance. (2) Serum insulin increased before an appreciable rise in serum glucose occurred. (3) Due to a greater rise in insulin than in glucose, the glucose/insulin ratio decreased. (4) After two days of injection the increase in serum insulin was most pronounced in those dogs that exhibited hyperglycemia and glycosuria. (5) Serum FFA increased greatly after one day of injection and remained high. During this growth hormone treatment, in one hour after injection of growth hormone with the ingestion of a meal, serum insulin rose, with lesser rise in glucose (further decrease in glucose/insulin), and fall in FFA. In the control period, however, no appreciable changes in serum insulin or glucose occurred following a meal. During daily growth hormone treatment, following glucose infusion: (1) Mean peak concentrations of serum insulin increased sevenfold in four days. (2) The rate of regression of serum insulin decreased. (3) Areas under the serum insulin curves increased up to tenfold the control value. (4) The mean rate of regression of serum glucose decreased, from the control value k — 4.28 per cent to —1.14 per cent after seven days. (5) The serum glucose/insulin ratio was unaltered, although the initial (fasting) values decreased. (6) The decline in serum FFA in 15 to 30 min. was more marked, but the levels remained above control. The changes in glucose/insulin indicate that growth hormone administration altered homeostatic control of pancreatic beta cells, such that at any given concentration of glucose in blood a greater rate of insulin secretion occurred. It is concluded that the “hyperinsulinemia” induced by the daily administration of growth hormone was associated with sustained increase in insulin secretion, and with augmentation of insulin secretion in response to a meal and to the infusion of glucose.

Effects of growth hormone on glucose utilization in fasted rats.

A single injection of growth hormone to fasted rats leads to a hypoglycemic response. Using a method of determination of rate of glucose utilization recently developed it can be shown that this hypoglycemic response is due to an increase in glucose utilization. Pretreatment of the animals with growth hormone decreases the response to a subsequent injection both as regards hypoglycemic reaction and as regards increase in glucose utilization.

Anterior pituitary growth hormone and blood sugar levels of normal and diabetic dogs.

In a study of blood sugar levels in 17 normal and 11 totally depancreatized dogs many experiments have been performed in an attempt to determine the mechanisms which cause the differences in response to a single injection of highly purified growth hormone preparations. The sugar level of the depancreatized but not of the normal dog is very sensitive to a single injection of growth hormone. When the hormone preparation is administered to a diabetic dog with a relatively low blood sugar level, i.e. well below 200 mg % an immediate rise is produced. At a preinjection level well above 200 mg % a temporary fall of the blood sugar occurs. The rise in blood sugar was prevented by blocking the adrenergic system with dihydroergotamine. It has therefore been concluded that growth hormone stimulates the adrenergic system and that the initial rise in blood sugar is probably the result of breakdown of glycogen in the liver. The initial fall in blood sugar due to growth hormone can be obtained in fasting depancreatized animals kept without insulin for 24 hours. The fall is less pronounced in animals kept without insulin for from 72–96 hours and is completely abolished when the dogs have been twice ‘pretreated’ with large doses of growth hormone. These results indicate as definitely as this indirect method of approach can that the blood sugar lowering effect of growth hormone preparations is intimately associated with the presence of insulin in the body.