Structure-Activity Relationships of a Synthetic Pentapeptide that Specifically Releases Growth Hormone<i>in Vitro</i>*

Bowers, Cyril Y.; Momany, Frank A.; Reynolds, G. A.; Chang, Ding; Hong, Anita; Chang, Kwen-Jen

doi:10.1210/endo-106-3-663

Cited by 207 publications

(91 citation statements)

References 16 publications

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“…(GHRP) which belongs to a series of synthetic GH-releasing pentapeptides and hexapeptides (GHRPs), has been shown to specifically stimulate GH release, both in vivo and in vitro in rats [5][6][7][8]. GHRPs were designed and derived from enkephalin through computer-modeling techniques [9].…”

Section: Somatostatin Pituitary Cellmentioning

confidence: 99%

Effect of Growth Hormone (GH)-Releasing Peptide (GHRP) on the Release of GH from Cultured Anterior Pituitary Cells in Cattle.

1994

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Section: Somatostatin Pituitary Cellmentioning

confidence: 99%

Effect of Growth Hormone (GH)-Releasing Peptide (GHRP) on the Release of GH from Cultured Anterior Pituitary Cells in Cattle.

1994

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“…In addition, a group of artificial molecules known as GH secretagogues (GHSs) stimulates GH release (Bowers et al 1980, 1984) via a 'novel' receptor, the GH secretagogue receptor (GHSR). The full-length GHSR, namely GHSR1a, is a G-protein-coupled receptor, which was first isolated from human and porcine pituitary cDNA libraries (Howard et al 1996).…”

Section: Introductionmentioning

confidence: 99%

Molecular cloning and mRNA expression analysis of two GH secretagogue receptor transcripts in orange-spotted grouper (Epinephelus coioides)

Chen

Tang²,

Yan³

et al. 2008

Journal of Endocrinology

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GH secretagogue receptor (GHSR) is the receptor of ghrelin, a circulating GH-releasing and appetite-inducing hormone. In this paper, two Ghsr cDNAs, gpGhsr1a and gpGhsr1b, were identified and characterized in a teleost, the orange-spotted grouper (Epinephelus coioides). The gpGHSR1a is 1512 bp in length with an open reading frame (ORF) that encodes a protein of 383 amino acids with seven transmembrane (TM) domains, while the 1703 bp gpGHSR1b contains an ORF encoding for 303 amino acids with five TM domains. Comparison between cDNA and gene sequences showed that the two transcripts are two alternative splicing forms of a single gpGhsr gene. Tissue distribution and ontogeny of two gpGhsr mRNAs were examined by RT-PCR. The gpGHSR1a is mainly expressed in brain and pituitary gland, when compared with a more widespread expression of gpGHSR1b. During embryonic and larval development, the gpGhsr1b mRNA appears before the gpGhsr1a mRNA. Furthermore, quantitative real-time PCR performed on brain showed that both transcripts have the highest expression level in the pituitary gland. The expression level of gpGHSR1a was generally higher than that of gpGHSR1b. GHSR expressing cells were also detected widely in grouper brain by in situ hybridization, with a broader distribution than previous reports in mammals. Finally, an in vitro study showed that expression of both gpGHSR transcripts in pituitary and hypothalamus is downregulated by GH and ghrelin but not by des-acyl ghrelin, and this suggests that feedback regulation of GHSR also exists in teleostean fishes.

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“…His--Trp-Ala-Trp--Phe-Lys-NH 2 (GHRP-6) was the first of these small peptides found to specifically release GH in vitro (Bowers et al 1980, Badger et al 1984, Sartor et al 1985a) and in vivo in a variety of species (Sartor et al 1985b, Ilson et al 1989, Walker et al 1990, Malozowski et al 1991, Hartman et al 1992. More recently, our group has reported the bioactivity of a new GHRP, His--2methyl-Trp-Ala--Phe-Lys-NH 2 (hexarelin) which is biologically active when given i.v., s.c. or orally in conscious adult rats (Conley et al 1994(Conley et al , 1995 and which may be a more potent GH secretagogue than GHRP-6 (Conley et al 1995).…”

Section: Introductionmentioning

confidence: 99%

Effects of repeated doses and continuous infusions of the growth hormone-releasing peptide hexarelin in conscious male rats

Conley

Gaillard²,

Giustina³

et al. 1998

Journal of Endocrinology

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We have previously shown that hexarelin, a novel GHreleasing peptide (GHRP), is able to elicit GH release when administered i.v., s.c. or by mouth and that it is a more potent GH secretagogue than GHRP-6. In the current study, we investigated the effects of hexarelin administered as repeated doses at 2 h intervals or as a continuous 6, 30 or 174 h infusion to conscious male rats.In the first experiment, adult male Sprague-Dawley rats were prepared with dual indwelling jugular catheters. On the day of experimentation, these animals received three 25 µg/kg i.v. boluses of hexarelin at 2 h intervals with blood sampling at 5, 10, 15, 30, 60, 90 and 120 min after each dose. The mean peak GH response and the mean area under the GH response curve (AUC) for the 30 min after each administration were calculated and are reported as the mean ... For both the peak and AUC results there was a significant (P<0·05) difference in the GH response noted between the first (peak 301 37 ng/ml; AUC 5585 700 ng/ml per 30 min) and second (peak 149 47 ng/ml; AUC 3056 908 ng/ml per 30 min) injections of hexarelin, but not between the first and third (peak 214 49 ng/ml; AUC 3862 844 ng/ml per 30 min). In a second series of experiments, adult male Sprague-Dawley rats received continuous infusions (100 µg/h) of hexarelin or saline (1 ml/h) for 6, 30 or 174 h. Blood samples were collected every 20 min for the duration of the 6 h infusion and for the last 6 h of the two longer hexarelin infusions. Plasma GH concentrations peaked within 40 min of the initiation of infusion, but soon returned to basal levels. Mean plasma GH concentrations did not differ between any of the treatment groups, nor did any of the parameters of pulsatile hormone release analyzed. No significant differences in plasma corticosterone concentrations were noted between any of the treatment groups. On the other hand, while neither the 6 h (941 70 ng/ml) nor the 30 h (954 70 ng/ml) hexarelin infusions resulted in a significant increase in the plasma IGF-I concentrations over those noted in the saline controls (935 65 ng/ml), a 174 h hexarelin infusion did elicit a significant increase (1289 42 ng/ml; P<0·05). Thus it appears that, while continuous exposure to hexarelin does not disrupt normal GH cycling, it may (after up to 174 h of exposure) alter other components of the growth axis. In addition, since the character of pulsatile GH release remained unaltered in response to the hexarelin infusion, it appears that this GHRP may not act by suppression of functional somatostatin tone as has been suggested previously.

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Structure-Activity Relationships of a Synthetic Pentapeptide that Specifically Releases Growth Hormonein Vitro*

Cited by 207 publications

References 16 publications

Effect of Growth Hormone (GH)-Releasing Peptide (GHRP) on the Release of GH from Cultured Anterior Pituitary Cells in Cattle.

Effect of Growth Hormone (GH)-Releasing Peptide (GHRP) on the Release of GH from Cultured Anterior Pituitary Cells in Cattle.

Molecular cloning and mRNA expression analysis of two GH secretagogue receptor transcripts in orange-spotted grouper (Epinephelus coioides)

Effects of repeated doses and continuous infusions of the growth hormone-releasing peptide hexarelin in conscious male rats

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