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GHRP-2 (pralmorelin) is a synthetic oligopeptide studied as a growth hormone secretagogue that acts through the ghrelin receptor GHS-R1a to modulate growth hormone secretion.
A synthetic hexapeptide growth hormone secretagogue (GHS) called Growth Hormone-Releasing Peptide-2 (GHRP-2) was created for experimental research on ghrelin-receptor signaling and growth hormone control. GHRP-2 functions primarily as an agonist of the growth hormone secretagogue receptor type 1a (GHS-R1a/GHSR), a class A G-protein-coupled receptor that is also activated by the endogenous hormone ghrelin, in contrast to growth hormone-releasing hormone (GHRH) analogs.
GHRP-2 belongs to a group of artificial growth hormone-releasing peptides that were created before to the identification of ghrelin. It differs from naturally occurring peptide hormones in that its structure includes non-natural amino acid residues, which also contribute to its distinctive stability and receptor-binding characteristics.
The hypothalamic-pituitary growth hormone axis has been the main focus of experimental research on GHRP-2. GH secretion-related signaling in the hypothalamus and pituitary systems can be stimulated by GHS-R1a activation. Although interactions between both regulatory pathways have been thoroughly studied, GHRPs function through a different receptor system than the traditional GHRH receptor.
Beyond GH secretion, GHRP-2 has been used experimentally to investigate ghrelin-receptor pharmacology, neuroendocrine signaling, appetite-associated pathways and metabolic responses. Preclinical studies have also explored additional GHS-R1a-dependent cellular processes. GHRP-2 has been directly characterised in the scientific literature as a synthetic agonist of the ghrelin receptor.
Overall, rather of being a naturally occurring hormone or GHRH analog, GHRP-2 is better described as a synthetic GHS-R1a agonist and experimental growth hormone secretagogue. It is a valuable study chemical for examining the molecular control of GH secretion and the broader ghrelin/GHSR signaling system due to its established receptor pharmacology.
Six amino acid residues make up the synthetic hexapeptide GHRP-2, which has the following sequence: H-D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH₂. Its structure sets it apart from naturally occurring hormones by combining two D-amino acids with the non-proteinogenic residue D-2-naphthylalanine (D-2-Nal). Instead of ending as a free carboxylic acid, the C-terminus is amidated.
The uncomplexed peptide has a molecular formula of C₄₅H₅₅N₉O₆ and a molecular weight of approximately 817.97–818.0 Da. GHRP-2 is also known chemically as pralmorelin and has the CAS Registry Number 158861-67-7.
Structurally, GHRP-2 is a relatively small, linear peptide without disulfide bonds or glycosylation. Its aromatic 2-naphthylalanine, tryptophan and phenylalanine residues contribute substantial hydrophobic character, while lysine and the N-terminal amino group provide ionisable functionality. Its charge and solubility therefore depend on factors such as pH, counter-ion and formulation.
GHRP-2 differs from typical endogenous L-amino acid peptides in its molecular effects due to the inclusion of D-configured and non-natural residues as well as C-terminal amidation. These structural characteristics are also required for analytically confirming GHRP-2; mass spectrometry and RP-HPLC are frequently employed to validate molecular identification and chromatographic purity.
GHRP-2 has been studied primarily as an agonist of the growth hormone secretagogue receptor type 1a (GHS-R1a/GHSR), a G protein-coupled receptor expressed in pituitary and hypothalamic systems involved in growth hormone regulation. This receptor is also the endogenous target of ghrelin. GHRP-2 therefore functions through a signaling system distinct from the classical growth hormone-releasing hormone (GHRH) receptor.
GHS-R1a Activation
Gαq/11-dependent signaling is mostly linked to GHS-R1a activation. This increases intracellular Ca2+ levels and produces intracellular second messengers, such as inositol trisphosphate (IP3), by stimulating phospholipase C (PLC). Because elevated intracellular calcium aids in the exocytotic release of stored growth hormone, calcium mobilization is especially important for pituitary somatotrophs. Blocking voltage-dependent Ca2+ channels has been shown in experimental GHRP-2 investigations to decrease GH secretion triggered by GHRP-2.
Growth Hormone Secretory Pathways
Pituitary cell studies have demonstrated that GHRP-2 can directly stimulate GH secretion from somatotrophs. Experimental research has also reported changes in GH mRNA and expression of genes associated with GH regulation, including GHS-R, GHRH-R and Pit-1.
Interaction with GHRH Signaling
The way GHRP-2 interacts with the GHRH pathway is a key aspect of GHRP-2 studies. Combined stimulation may result in elevated or synergistic GH responses, even though GHRP-2 and GHRH function through different receptor systems. Pituitary cell systems and human endocrine investigations have explored this link.
Overall, GHRP-2 is best characterised mechanistically as a GHS-R1a agonist that influences intracellular calcium-dependent signalling and growth-hormone secretion. Its effects occur within a wider neuroendocrine network involving GHRH, somatostatin and endogenous ghrelin signaling, and the relative contribution of these pathways can vary between experimental models.
This summary reflects findings reported in published preclinical and in vitro research. The original studies supporting this information are listed in the references.
GHRP-2 is widely used as an experimental agonist of the growth hormone secretagogue receptor (GHS-R1a), the receptor also activated by endogenous ghrelin. Receptor-based studies investigate ligand binding, receptor activation and downstream signalling to better understand how synthetic growth hormone secretagogues interact with the ghrelin receptor system.
A major area of GHRP-2 research involves pituitary somatotroph cells, which synthesise and secrete growth hormone. Primary pituitary-cell studies have examined GHRP-2-induced membrane depolarisation, changes in intracellular Ca²⁺ and subsequent GH secretion. Electrophysiological studies in cultured ovine somatotrophs demonstrated GHRP-2-associated changes in membrane calcium permeability and electrical activity.
Experimental studies have used GHRP-2 to investigate the regulation and dynamics of growth hormone release. Research has compared responses to GHRP-2 with those produced by GHRH and other growth hormone secretagogues, examining variables such as dose, age and neuroendocrine status. Human experimental studies have demonstrated dose- and age-dependent differences in GH responses.
Growth hormone-releasing hormone (GHRH) and GHRP-2 work thru distinct receptor systems, hence their interactions offer a crucial experimental model for researching GH regulation. Research looks at how somatotroph signaling and secretory responses are altered when GHS-R1a and GHRH receptors are activated simultaneously.
GHRP-2 research has investigated calcium mobilisation and membrane ion-channel activity as intracellular mechanisms associated with GH secretion. Electrophysiological experiments have shown that GHRP-2 can depolarise somatotroph membranes and promote Ca²⁺-dependent electrical activity, providing a cellular model for investigating secretagogue-induced hormone release.
Independent of its GH-secretagogue effect, GHRP-2, a synthetic agonist of the ghrelin receptor, has also been used to study hunger and food-intake signaling. Human research demonstrated improved food intake during experimental GHRP-2 administration, implying its application as a pharmacological probe of ghrelin-associated eating circuits.
GHRP-2 research is not restricted to GH. Experimental human studies have also measured ACTH, cortisol and prolactin responses following GHRP-2 exposure. These investigations are important for defining the endocrine selectivity of the peptide, as GHRP-2 has produced smaller but measurable effects on hormonal systems outside the GH axis.
GHRP-2 has been compared with GHRH and other synthetic growth hormone-releasing peptides, including hexarelin, to better understand differences in their potency and endocrine responses. By studying these compounds under controlled experimental conditions, researchers can identify which effects are more closely associated with GHRP-2 and which are shared across the wider growth hormone secretagogue family. These comparative studies also provide useful insight into differences in receptor activity, growth hormone release and broader neuroendocrine responses.
Both peptide identification and chromatographic purity should be confirmed by analytical verification of GHRP-2 (pralmorelin). Purity can be evaluated and synthesis-related contaminants, such as shortened or deleted sequences, can be found using reverse-phase HPLC (RP-HPLC). Chromatographic purity should be backed up by an independent analytical method since it does not prove molecular identification on its own.
GHRP-2 can be validated using LC-MS or high-resolution mass spectrometry by comparing the observed molecular mass with the expected value. The uncomplexed peptide has a molecular weight of about 818.0 Da, however salt variants may have different analytical characteristics. Published techniques for identifying GHRP-2 have also demonstrated the use of liquid chromatography combined with electrospray-ionization tandem mass spectrometry (LC-ESI-MS/MS).
Sequence-related fragmentation information can be provided by MS/MS when additional verification is needed. The required GHRP-2 sequence, purity, observed molecular mass, analytical methods, batch identification, and pertinent acceptance criteria should all be documented in a batch-specific Certificate of Analysis.
Store GHRP-2 at 2–8°C and protect it from light and moisture. Keep the vial sealed during storage and avoid prolonged exposure to elevated temperatures.
Before opening a refrigerated vial, allow the sealed vial to reach room temperature to minimise condensation. Handle the material under appropriate laboratory conditions and minimise unnecessary exposure to air, moisture, and light. Avoid repeated freeze–thaw cycles.
GHRP-2 is a synthetic hexapeptide and is not a naturally occurring human peptide hormone. It was developed as part of the growth hormone-releasing peptide family and contains non-natural structural features, including D-amino-acid residues, which distinguish it from endogenous peptides such as ghrelin.
Yes. Pralmorelin is an alternative name for GHRP-2 and refers to the same synthetic growth hormone secretagogue. The compound has also appeared in research literature under development identifiers such as KP-102.
GHRP-2 incorporates D-configured amino acids as part of its synthetic design. These residues contribute to its molecular conformation and receptor-binding characteristics and can also make the peptide less susceptible to degradation by certain proteolytic enzymes that preferentially recognise natural L-amino-acid peptides.
GHRP-2 acts principally as an agonist of the growth hormone secretagogue receptor type 1a (GHS-R1a), also known as the ghrelin receptor. Activation of this G-protein-coupled receptor has been extensively investigated in relation to pituitary growth-hormone secretion and hypothalamic signaling.
GHRP-2 and GHRH stimulate growth-hormone-associated pathways through different receptors. GHRP-2 acts through GHS-R1a, whereas GHRH binds to the GHRH receptor (GHRHR). This distinction is necessary because the two receptor systems use overlapping but different intracellular mechanisms and can interact synergistically in research models.
GHS-R1a activation is primarily associated with Gαq/11–phospholipase C signaling, leading to production of intracellular second messengers and mobilisation of Ca²⁺. In pituitary somatotrophs, these calcium-dependent processes contribute to growth-hormone secretion. Experimental work has also examined changes in expression of GHS-R, GHRH-R, Pit-1 and GH-associated genes following GHRP-2 exposure.
GHRP-2 and GHRH are frequently investigated together because combined stimulation can produce a greater GH response than either secretagogue alone. This synergistic behaviour has been demonstrated in experimental animal and human studies and provides a useful model for investigating interactions between GHS-R1a and GHRH-receptor signalling within the GH regulatory system.
Although both GHRP-2 and GHRP-6 are synthetic growth hormone-releasing peptides that function via GHS-R1a, their pharmacological characteristics and amino acid sequences differ. The two peptides should not be regarded as molecularly or pharmacologically equivalent because experimental studies have shown variations in receptor potency and endocrine responses.
GHRP-2 is provided for laboratory research and scientific investigation only. It is not for human consumption or veterinary use and is not intended for administration. It is not intended to diagnose, treat, cure, or prevent any disease or medical condition. The information on this page is provided for scientific research purposes only.
