Growth hormone (GH)-releasing peptide-6 requires endogenous hypothalamic GH-releasing hormone for maximal GH stimulation.
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TL;DR: GH-releasing peptide-6 (GHRP-6) is a potent GH secretagogue that releases GH by uncertain mechanisms and the specific antagonist to GHRH (N-Ac-Tyr1,D-Arg2)GHRH(1-29)NH2 (G HRH Ant) shows that endogenous G HRH is necessary for most of the GH response to G HRP- 6 in humans.
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Abstract: GH-releasing peptide-6 (GHRP-6) is a potent GH secretagogue that releases GH by uncertain mechanisms. To assess whether GHRH is required for GH release by GHRP-6 in humans, we used the specific antagonist to GHRH (N-Ac-Tyr1,d-Arg2)GHRH(1–29)NH2 (GHRH Ant). We have previously shown that GHRH-Ant (400 μg/kg) blocked the GH response to 0.33 and 3.3 μg/kg boluses of GHRH by 95% and 81%, respectively. Nine healthy men between the ages of 20 and 30 yr were studied on two occasions. They received either saline or GHRH-Ant (400 μg/kg, iv) at 0840 h, followed by GHRP-6 (1μ g/kg, iv bolus) at 0900 h. Blood was sampled every 10 min from 0800–1100 h. GH responses were measured as the maximal increase over the baseline GH concentration and as the area under the curve. GHRH-Ant eliminated most of the GH response to GHRP-6 [maximal increase over the baseline GH concentration, 33.8 ± 4.8 vs. 6.2 ± 1.8 μg/L (mean ±sem; P< 0.0001); area under the curve, 1701 ± 278 vs. 376 ± 113 μg/min·L (P < 0.001)]. These data show that e...
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Citations
Stomach Is a Major Source of Circulating Ghrelin, and Feeding State Determines Plasma Ghrelin-Like Immunoreactivity Levels in Humans
Hiroyuki Ariyasu,Kazuhiko Takaya,Tetsuya Tagami,Yoshihiro Ogawa,Kiminori Hosoda,Takashi Akamizu,Michio Suda,Toshikiyo Koh,Koshi Natsui,Shigetake Toyooka,Gotaro Shirakami,Takeshi Usui,Akira Shimatsu,Kentaro Doi,Hiroshi Hosoda,Masayasu Kojima,Kenji Kangawa,Kazuwa Nakao +17 more
TL;DR: It is concluded that the stomach is a major source of circulating ghrelin and that plasma gh Relin-like immunoreactivity levels reflect acute and chronic feeding states in humans.
Biological, physiological, pathophysiological, and pharmacological aspects of ghrelin.
TL;DR: Ghrelin is considered a gastrointestinal peptide contributing to the regulation of diverse functions of the gut-brain axis and there is indeed a possibility that ghrelin analogs, acting as either agonists or antagonists, might have clinical impact.
Pathophysiology of the neuroregulation of growth hormone secretion in experimental animals and the human
TL;DR: The pathophysiology of the GHRH somatostatin-GH-IGF-I feedback axis is reviewed and it is proposed that this system is best viewed as a multivalent feedback network that is exquisitely sensitive to an array of neuroregulators and environmental stressors and genetic restraints.
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Ghrelin--a hormone with multiple functions.
TL;DR: Ghrelin is a brain-gut peptide with growth hormone-releasing and appetite-inducing activities as mentioned in this paper, which is mainly secreted from the stomach mucosa but it is also expressed widely in different tissues and therefore may have both endocrine and paracrine effects.
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Biologic activities of growth hormone secretagogues in humans.
Ezio Ghigo,Emanuela Arvat,Roberta Giordano,Fabio Broglio,Laura Gianotti,Mauro Maccario,Gianni Bisi,Andrea Graziani,Mauro Papotti,Giampiero Muccioli,Romano Deghenghi,Franco Camanni +11 more
TL;DR: Growth hormone secretagogues are synthetic peptidyl and nonpeptidyl molecules with strong, dose-dependent, and reproducible growth hormone (GH)-releasing activity even after oral administration, and ghrelin, a 28 amino acid peptide synthesized in the stomach but also in other tissues, has opened new fascinating perspectives of research in this field.
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References
A Receptor in Pituitary and Hypothalamus That Functions in Growth Hormone Release
Andrew D. Howard,Scott D. Feighner,Doris F. Cully,Joseph P. Arena,Paul A. Liberator,Charles Rosenblum,Michel J. Hamelin,Donna L. Hreniuk,Oksana C. Palyha,Jennifer W. Anderson,Philip S. Paress,Carmen Diaz,Michael Chou,Ken K. Liu,Karen K. McKee,Sheng-Shung Pong,Lee-Yuh Chaung,Alex Elbrecht,Mike Dashkevicz,Robert P. Heavens,Michael Rigby,Dalip J. S. Sirinathsinghji,Dennis C. Dean,David G. Melillo,Arthur A. Patchett,Ravi P. Nargund,Patrick R. Griffin,Julie A. DeMartino,Sunil Gupta,James M. Schaeffer,Roy G. Smith,Lex H.T. Van der Ploeg +31 more
TL;DR: A heterotrimeric GTP-binding protein (G protein)-coupled receptor (GPC-R) of the pituitary and arcuate ventro-medial and infundibular hypothalamus of swine and humans was cloned and was shown to be the target of the GHSs.
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On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone
TL;DR: [His1,Lys6] GHRP may be a valuable peptide for investigating the function of the pituitary somatotrophs and has the potential for increasing BW gain of a variety of normal animals by inducing GH release via a direct pituitsary site of action.
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On the Actions of the Growth Hormone-Releasing Hexapeptide, GHRP
TL;DR: Evidence indicates that these opiates and GHRP administered together synergistically release GH, demonstrating the independent action(s) ofGHRP and the opiates, and the complementary, rather dramatic synergistic interaction of G HRP, GHRH, and dermorphin or GHRp, G HRh, and 2549 in releasing GH again strongly supports the independent actions of these compounds.
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The growth hormone-releasing activity of a synthetic hexapeptide in normal men and short statured children after oral administration.
TL;DR: It has been shown that iv GH-releasing peptide (GHRP; His-DTrp-Ala-trp-DPhe-Lys-NH2) specifically releases GH in man, and five normal men were given GHRP orally at dosages of 100 and 300 micrograms/kg to consistently increase GH levels in adults.
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Plasma GH responses to GHRH and insulin-induced hypoglycemia in man
Tamotsu Shibasaki,Mari Hotta,Akitsugu Masuda,Toshihiro Imaki,Naoko Obara,Hiroshi Demura,Nicholas Ling,Kazuo Shizume +7 more
TL;DR: Results suggest that desensitization of G HRH 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 or insulin-induced hypoglycemia suppressed plasma GH responses to the following GHR H44 administration.
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Andrew D. Howard,Scott D. Feighner,Doris F. Cully,Joseph P. Arena,Paul A. Liberator,Charles Rosenblum,Michel J. Hamelin,Donna L. Hreniuk,Oksana C. Palyha,Jennifer W. Anderson,Philip S. Paress,Carmen Diaz,Michael Chou,Ken K. Liu,Karen K. McKee,Sheng-Shung Pong,Lee-Yuh Chaung,Alex Elbrecht,Mike Dashkevicz,Robert P. Heavens,Michael Rigby,Dalip J. S. Sirinathsinghji,Dennis C. Dean,David G. Melillo,Arthur A. Patchett,Ravi P. Nargund,Patrick R. Griffin,Julie A. DeMartino,Sunil Gupta,James M. Schaeffer,Roy G. Smith,Lex H.T. Van der Ploeg +31 more