Growth hormone releasing factors.
Explore the source record for details and available documents.
Adenoma, Islet Cell↗
Biomedical subjects
N Ling
Publications and source records attributed to N Ling.
Physiological studies with somatocrinin, a growth hormone-releasing factor.
Explore the source record for details and available documents.
Animals↗
Immunohistochemical localization and radioimmunoassay of corticotropin-releasing factor in the forebrain and hypophysis of the frog Rana ridibunda.
The distribution of immunoreactive corticotropin-releasing hormone (CRF) in the forebrain and pituitary of the frog Rana ridibunda was studied by means of specific radioimmunoassay and immunohistochemistry using the indirect immunofluorescence and the peroxidase-antiperoxidase techniques. Relatively high concentrations of CRF-like material were found in both chiasmatic and infundibular regions of the hypothalamus (352 +/- 11 and 422 +/- 36 pg, respectively). Large amounts of CRF were also found in neurointermediate lobe extracts. Standard curves of synthetic CRF and the dilution curves for hypothalamic or neurointermediate lobe extracts were parallel. After Sephadex G-75 gel filtration, CRF-like immunoreactivity eluted in a single peak, in the same position as synthetic ovine CRF. Reversed-phase high-performance liquid chromatography of the material purified on Sephadex G-75 revealed 5 components with CRF-like immunoreactivity. The major peak had a retention time of 22 min as compared to 25.4 min for ovine CRF and 36 min for rat CRF. The detection of CRF-like immunoreactivity in neurons was facilitated by colchicine pretreatment of the frogs. The great majority of the CRF-positive perikarya were seen in the ventral region of the preoptic nucleus. A few scattered perikarya were also observed in the dorsal preoptic nucleus and in the retrochiasmatic region. Immunoreactive fibers were found in the infundibular nucleus and in various extrahypothalamic zones. CRF-containing neurons were apparently distinct from mesotocinergic and vasotocinergic neurons. A large number of immunoreactive nerve fibers were observed in the median eminence in close contact with the capillaries of the pituitary portal plexus and in the neural lobe. A few CRF-positive fibers were detected in the intermediate lobe, whereas the distal lobe was totally negative. These results show that the diencephalon and pars intermedia-nervosa of the frog contain a peptide immunologically related to mammalian CRF.
Animals↗
Pituitary secretion of growth hormone in response to opioid peptides and opiates is mediated through growth hormone-releasing factor.
Passive immunization of rats with an antiserum raised against rat growth hormone-releasing factor (GRF) completely inhibited the growth hormone (GH) response to morphine and beta-endorphin but did not alter the prolactin (PRL) response to those two stimuli. These results demonstrate that opiate and opioid peptide stimulation of pituitary GH secretion is mediated through hypothalamic GRF and presents an animal model in which the stimulated secretion of GH and PRL can be specifically dissociated.
Animals↗
Plasma growth hormone response to human growth hormone releasing factor in rats administered with chlorpromazine and antiserum against somatostatin. Effects of hypo- and hyperthyroidism.
The effect of hypo- and hyperthyroidism on the plasma growth hormone (GH) response to synthetic human growth hormone releasing factor (GRF) was determined in conscious, freely moving rats pretreated with chlorpromazine and antiserum against somatostatin. Chlorpromazine plus somatostatin antiserum pretreated rats gave consistent response to GRF which was not observed in untreated rats. Chlorpromazine alone has no effect on GH secretion induced by GRF in rat pituitary monolayer culture. In rats made hypothyroid by thyroidectomy, both basal and peak plasma GH responses to a small (0.25 microgram/kg bw) and a moderate dose of GRF (1 microgram/kg bw) were significantly reduced as compared to controls. In rats made hyperthyroid by the administration of thyroxine, basal and peak plasma GH responses to a small but not to a moderate dose of GRF were significantly reduced as compared to controls. A reduced plasma GH response to a small dose of GRF was observed 8 days after the cessation of thyroxine administration. The pituitary GH reserve was markedly reduced in hypothyroid but not in hyperthyroid rats as compared to their respective controls. These results indicate that plasma GH response to GRF is reduced both in hypo- and hyperthyroidism. The mechanism involved in the phenomenon appears to be different between the two conditions.
Animals↗
Regional distribution of rat growth hormone releasing factor-like immunoreactivity in rat hypothalamus.
A heterologous RIA for rat GH-releasing factor (rGRF) was established using synthetic rGRF-(1-43)OH for both standard reference and radioiodination with the antiserum produced against human GRF-(1-44) NH2. The regional distribution of rGRF-like immunoreactivity (LI) in rat hypothalamus was examined according to the Palkovits microdissection method and compared with that of somatostatin (SRIF)-LI. Both rGRF- and SRIF-LI contents (mean +/- SE; nanograms per mg protein) were highest in the median eminence (rGRF, 32.28 +/- 11.42; SRIF, 109.9 +/- 19.2) and next most abundant in the arcuate nucleus (rGRF, 3.50 +/- 0.47; SRIF, 12.88 +/- 0.60). Only a small amount of rGRF-LI was found in the ventromedial (1.41 +/- 0.51) and dorsomedial (1.16 +/- 0.15) nuclei and the anterior hypothalamic area (1.29 +/- 0.42), whereas rGRF-LI was not detected in the other nuclei of the hypothalamus. A considerable amount of SRIF-LI was contained in the periventricular, ventromedial, and paraventricular nuclei and the anterior hypothalamic area, in accordance with other reports. Gel filtration chromatography revealed that hypothalamic extracts contained a major peak of rGRF-LI corresponding to rGRF-(1-43)OH and two peaks of SRIF-LI equivalent to SRIF-(1-28) and SRIF-(1-14), respectively. These findings indicate that rGRF-LI is localized in the median eminence and arcuate nucleus in the rat and that rGRF-, SRIF-(1-28)-, and SRIF-(1-14)-LI are present in a 1:2.10:6.29 ratio on a molar basis.
Animals↗
Immunoreactive and biologically active growth hormone-releasing factor in the rat placenta.
Rat placentas from fetuses of 18 and 20 days of gestation were collected, extracted, and examined for their capacity to stimulate GH release in vitro. The crude extract stimulated, in a dose-dependent fashion, GH release by rat anterior pituitary cells in monolayer culture. The biological and immunological activities retained on antirat GH-releasing factor immunoaffinity columns eluted on Sephadex G-75 (fine) columns with an estimated mol wt of 5000 daltons. Reverse phase HPLC of this material revealed the presence of two forms of GRF activity that eluted with retention times identical to those of synthetic rat GRF and its methionine sulfoxide counterpart [Met(O)27]GRF. The results demonstrate the presence of an immunoreactive and biologically active GRF in the rat placenta that is indistinguishable from rat hypothalamic GRF.
Animals↗
The effect of free fatty acids on growth hormone (GH)-releasing hormone-mediated GH secretion in man.
The effect of FFA on GH-releasing hormone (GHRH)-mediated secretion of GH was examined in six normal young men. Three of the men were infused with 250 ml of a lipid-heparin solution at 1.67 ml/min for 150 min, and the other three were given an equivalent volume of saline in the same manner. Thirty minutes after the start of infusion, 100 micrograms GHRH (the 44-amino acid form) were injected iv, and plasma GH and FFA were measured. One week later, the same men participated in an identical experiment, but the ones who had received lipid-heparin previously were given saline and vice versa. In both experiments, plasma FFA increased to 2.25 +/- 0.16 meq/liter (mean +/- SEM) 60 min after the start of lipid-heparin infusion, whereas FFA levels did not change significantly in the saline-treated group. Mean plasma GH levels reached peak concentrations in both groups 30 min after GHRH treatment. However, the peak GH response when lipid-heparin was given was significantly diminished (8.4 +/- 1.7 ng/ml), compared with the peak response when saline was given (28.9 +/- 7.1 ng/ml). These data suggest that plasma FFA elevations induced by lipid-heparin infusion inhibit GH secretion induced by GHRH.
Adult↗
The effect of glucose on growth hormone (GH)-releasing hormone-mediated GH secretion in man.
The effect of glucose on GH-releasing hormone (GHRH)-mediated GH secretion was examined in six normal young men. In two paired experiments, the six men drank a 75-g glucose solution or an equal volume of water 30 min before receiving, iv, 100 micrograms of the 44-amino acid form of human pancreatic GHRH (hGHRH-44). One week later, the same men underwent an identical experimental protocol in a cross-over trial. Basal plasma GH concentrations before hGHRH-44 administration were not statistically different in the two experiments [glucose experiment, 2.1 +/- 0.1 (+/- SE) ng/ml; water experiment, 2.6 +/- 0.6 ng/ml]. The mean peak plasma GH level occurred 30 min after hGHRH-44 administration in both experiments. However, the mean GH response was significantly diminished when the men received glucose (8.12 +/- 1.12 ng/ml) compared to that when they received only water (23.70 +/- 8.46 ng/ml; P less than 0.01). Thus, hyperglycemia may exert an inhibitory effect on the plasma GH response to hGHRH-44.
Adult↗
Plasma GH responses to GHRH and insulin-induced hypoglycemia in man.
Changes in plasma GH levels in response to an intravenous bolus injection of 200 micrograms GHRH-44 or 0.1 U/kg body weight regular insulin were examined in normal men who were pre-treated with 200 micrograms GHRH-44 or 0.1 U/kg body weight regular insulin 120 min in advance. The prior bolus injection of GHRH-44 inhibited the plasma GH response to the subsequent administration of GHRH-44 whereas the plasma GH response to the subsequent injection of insulin was not influenced by the prior administration of GHRH-44. The prior administration of insulin attenuated the plasma GH response to the subsequently given GHRH-44. These results suggest that desensitization of GHRH receptors in somatotrophs and/or somatostatin hypersecretion induced by increase in plasma GH levels following the prior GHRH-44 administration may be involved in the mechanism by which the prior GHRH-44 administration or insulin-induced hypoglycemia suppressed plasma GH responses to the following GHRH-44 administration. Sudden suppression of somatostatin secretion, which causes rebound of GH secretion, may occur in insulin-induced hypoglycemia.
Adult↗
The use of the corticotropin-releasing hormone test to monitor the recovery of patients with Cushing's disease or Cushing's syndrome due to an adrenal adenoma after adenomectomy.
Six patients with Cushing's disease and three with Cushing's syndrome due to an adrenal adenoma were monitored after their adenomectomy with the corticotropin-releasing hormone test to evaluate the progress of recovery of their pituitary adrenal function. Before surgery the patients with Cushing's disease showed either high, normal or low responses of plasma ACTH and cortisol to 100 micrograms synthetic ovine corticotropin-releasing hormone (CRH) administered intravenously, whereas all three patients with Cushing's syndrome due to an adrenal adenoma showed no response of plasma ACTH or cortisol to CRH. One or two months after surgery, the patients who had Cushing's disease had low levels of basal plasma ACTH and cortisol and their responses to CRH were extremely low. However, the same patients were tested later, it was found that their responses to CRH gradually increased and reached normal ranges approximately within one year after tumor removal, which coincided with the overall improvement in their clinical signs and symptoms due to adrenal insufficiency. In contrast, the recovery of the pituitary adrenal function in patients who had Cushing's syndrome due to an adrenal adenoma was not complete even one year after surgery. Thus the corticotropin-releasing factor test is a useful criteria to evaluate the recovery of the pituitary adrenal function in these patients after surgery, since the responses of plasma ACTH and cortisol to the administered CRH are parallel with the improvements in clinical signs and symptoms due to adrenal insufficiency in patients with Cushing's disease.
Adenoma↗
The inter- and intra-subject variabilities of plasma GH response to human growth hormone-releasing hormone (1-44) NH2 in men.
The effects of intravenously given human growth hormone-releasing hormone (1-44) NH2 (hGRH-44) on growth hormone (GH) secretion were studied in normal men. A wide variability of intersubject GH response to hGRH-44 was observed. The peak plasma GH levels in response to 50, 100 and 200 micrograms hGRH-44 in 7 normal men were 9.1 +/- 3.2 ng/ml (Mean + SEM), 19.3 +/- 3.3 ng/ml and 22.4 +/- 4.0 ng/ml, respectively. Both the mean peak values for plasma GH response to 100 and 200 micrograms were significantly greater than that for 50 micrograms hGRH-44 injection (p less than 0.01), although there was no significant difference of the mean peak plasma GH values and mean concentrations at each time point, except for those at 120 min, when 100 or 200 micrograms hGRH-44 was administered. A significant difference in the mean amount of plasma GH secreted in response to hGRH-44 was observed only between 50 and 200 micrograms hGRH-44 injection (p less than 0.01). Furthermore, a dose-related plasma GH increase in response to hGRH-44 was not always observed in each subject. In contrast to the wide intersubject variability, the difference among responses of plasma GH to 100 micrograms or 200 micrograms of hGRH-44 given at multiple times separated by intervals of at least 1 week in each individual was relatively small.(ABSTRACT TRUNCATED AT 400 WORDS)
Adult↗
Rat hypothalamic growth hormone-releasing factor: isolation, sequence analysis and total synthesis.
Growth hormone-releasing factor (GRF) was isolated from acid extracts of approximately 35,000 rat hypothalami by means of immunoaffinity chromatography, gel filtration and two steps of reverse-phase HPLC. Amino acid analysis, gas-liquid phases sequencing and peptide mapping established that rat GRF is a 43 amino acid peptide with the amino acid sequence His-Ala-Asp-Ala-Ile-Phe-Thr-Ser-Ser-Tyr-Arg-Arg-Ile-Leu-Gly- Gln-Leu-Tyr-Ala-Arg-Lys-Leu-Leu-His-Glu-Ile-Met-Asn-Arg-Gln-Gln-Gly- Glu-Arg-Asn-Gln-Glu-Gln-Arg-Ser-Arg-Phe-Asn-OH, confirming the primary structure reported earlier (Spiess et al Nature 303, 532 (1983).
Amino Acid Sequence↗
Growth hormone-releasing factor from ovine and caprine hypothalamus: isolation, sequence analysis and total synthesis.
Peptides with high intrinsic growth hormone releasing activity (growth hormone-releasing factor, GRF) were isolated from 2100 ovine and 2600 caprine (goat) hypothalami by means of acid extraction, immunoaffinity chromatography, gel filtration and reverse phase HPLC. Structural characterization of the 44 amino acid ovine peptide by gas-liquid phase sequencing and peptide mapping established its primary structure as Tyr-Ala-Asp-Ala-Ile-Phe-Thr-Asn-Ser -Tyr-Arg-Lys-Ile-Leu-Gly-Gln-Leu-Ser-Ala-Arg-Lys-Leu-Leu-Gln-Asp-Ile-Met -Asn -Arg-Gln-Gln-GLy-Glu-Arg-Asn-Gln-Glu-Gln-Gly-Ala-Lys-Val-Arg-Leu-NH2. Caprine GRF was found to possess the same sequence except for the replacement of the isoleucine residue in position 13 with valine and thus is identical to bovine GRF.
Amino Acid Sequence↗
Neuropeptides derived from prosomatostatin that do not contain the somatostatin-14 sequence.
Two neuropeptides reacting with antibodies directed against the C-terminal region of somatostatin 28(1-12) were purified to homogeneity from rat brain extracts. Amino acid analysis revealed that the larger peptide (8 kdaltons) consisted of 76 amino acids. Microsequencing established its aminoterminal structure as: Ala-Pro-Ser-Asp-Pro-Arg-Leu-Arg-Gln-Phe-X-Gln-Lys. The 8 kdalton somatostatin 28(1-12)-like peptide corresponds to the whole prosomatostatin molecule without Arg-Lys-somatostatin-14. The smaller peptide (5 kdaltons) consists of 44 amino acids and is generated after cleavage of a Leu-Leu bond at position 56-57 of pre-prosomatostatin. Both 8 kdalton and 5 kdalton somatostatin 28(1-12)-like peptides contain somatostatin 28(1-12) at their C-termini. The 4 most abundant neuropeptides derived from pre-prosomatostatin (pre-proSS) and presently characterized are: somatostatin-14, somatostatin 28(1-12), somatostatin 28 and pre-proSS25-100.
Amino Acid Sequence↗
Synthesis and in vitro bioactivity of C-terminal deleted analogs of human growth hormone-releasing factor.
A series of C-terminal deleted analogs of human growth hormone-releasing factor (hGRF) with either an amidated or a free carboxylic acid C-terminus were synthesized by solid phase methodology. Their capacity to release growth hormone was tested on rat anterior pituitary cells in monolayer culture. A gradual decrease of bioactivity down to 23% relative to hGRF was noted when the C-terminal amino acids were deleted to hGRF (1-34)OH. Further deletions, however, did not decrease the bioactivity because the potencies of the fragments, hGRF(1-31)NH2, (1-30)NH2 and (1-29)NH2 remained at about 50% of that of hGRF. Continual deletion of residues to hGRF(1-23)NH2, (1-22)NH2 and (1-21)NH2 still yielded bioactive fragments with full intrinsic activity despite very low potency. Only with the deletion down to hGRF(1-19)NH2 did the bioactivity completely disappear. Thus, together with the data published in a previous paper (1), the minimal biologically active core of hGRF with full intrinsic activity comprises the fragment (3-21).
Animals↗
Distribution of immunoreactive growth hormone releasing factor(1-44)NH2 in the tuberoinfundibular system of the rhesus monkey.
Using an antiserum which reacts with the carboxyl terminus of GRF(1-44)NH2, the distribution of immunoreactive growth hormone releasing factor (GRF) in the rhesus monkey hypothalamus was delineated by peroxidase immunocytochemistry. Immunoreactive material was present in dense terminal fields in the median eminence closely associated with portal capillaries but in a location distinct from that noted for immunoreactive thyrotropin-releasing hormone (TRH) or somatostatin. GRF-immunoreactive cell bodies were identified in the arcuate nucleus and ventromedial nucleus. These studies provide evidence for the presence of GRF(1-44)NH2 in the primate brain and demonstrate that in the hypothalamus it is localized exclusively in cells and fibers corresponding to the tuberoinfundibular system.
Animals↗
Isolation and characterization of the bovine hypothalamic corticotropin-releasing factor.
A 41 amino acid peptide with high intrinsic corticotropin-releasing activity was isolated from 1000 bovine hypothalami by means of immunoaffinity chromatography, gel filtration, and two steps of reverse phase HPLC. The primary structure of the amino terminal 39 amino acids was characterized by gas phase sequence analysis. The sequence of the amidated carboxyl terminal dipeptide was established by digestion of the intact natural product with Staphylococcus aureus V8 protease, dansylation of the digest and comparative reverse phase liquid chromatography studies with the synthetic dansylated dipeptides Ile-Ala-NH2, Ile-Ala-OH, Ala-Ile-NH2 and Ala-Ile-OH. The complete structure of the bovine corticotropin-releasing factor was established as: Ser-Gln-Glu-Pro-Pro-Ile-Ser-Leu-Asp-Leu-Thr-Phe-His-Leu-Leu-Arg-Glu-Val- Leu- Glu-Met-Thr-Lys-Ala-Asp-Gln-Leu-Ala-Gln-Gln-Ala-His-Asn-Asn-Arg-Lys-Leu- Leu- Asp-Ile-Ala-NH2 using approximately 650 pmol of material.
Amino Acid Sequence↗