GH secretagogue peptides
GH secretagogue peptides are synthetic compounds that interact with growth hormone-releasing hormone receptors (GHRH-R) or ghrelin receptors (GHS-R1a) on pituitary somatotrophs to stimulate growth hormone release. Two distinct classes: GHRH analogs — CJC-1295, Sermorelin, Tesamorelin — activate GHRH receptors; GH secretagogues such as Ipamorelin activate ghrelin receptors. Published research characterizes these as G-protein coupled receptors (GPCRs) that stimulate adenylate cyclase and increase intracellular cAMP upon activation (PMID: 15775957).
GHRH receptor activation increases growth hormone synthesis and secretion through cAMP-dependent pathways. Ghrelin receptor activation triggers phospholipase C signaling, mobilizing intracellular calcium — a distinct mechanism from the GHRH pathway. These mechanisms have been characterized in pituitary cell cultures and animal models. Research applications focus on investigating pituitary function, receptor pharmacology, and growth hormone regulation. These peptides serve as tools for studying endocrine signaling, not as therapeutic agents.
How CJC-1295 variants differ
CJC-1295 exists in two forms that differ in pharmacokinetic properties. CJC-1295 without DAC (Drug Affinity Complex) — also called Modified GRF (1-29) — is a 29-amino acid GHRH analog with substitutions at positions 2, 8, 15, 16, 23, 24, and 28 that enhance metabolic stability. Published studies demonstrate these modifications increase half-life compared to native GHRH (PMID: 15775957).
CJC-1295 with DAC includes the same peptide sequence plus a DAC moiety that enables albumin binding, further extending duration. The DAC version has longer terminal half-life but slower onset. Published pharmacokinetic studies show that the DAC modification creates a circulating depot that gradually releases active peptide (PMID: 16452336). Both forms activate GHRH receptors through the same mechanism — increasing cAMP and stimulating growth hormone release. Research applications may prefer the non-DAC form for studies requiring shorter duration or the DAC form for extended release protocols.
Ipamorelin molecular structure
Ipamorelin is a synthetic pentapeptide with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2, where Aib is aminoisobutyric acid and D-2-Nal is D-2-naphthylalanine. Published research establishes the molecular formula as C₃₈H₄₉N₉O₅ with molecular weight 711.9 g/mol (PMID: 10698741). The peptide contains D-amino acids at positions 2-Nal and Phe, introducing proteolytic resistance. C-terminal amidation provides additional stability.
Published binding studies demonstrate that Ipamorelin selectively activates the ghrelin receptor (GHS-R1a) with high affinity while showing minimal activity at other pituitary hormone receptors including ACTH, prolactin, and cortisol pathways (PMID: 11916262). This selectivity distinguishes Ipamorelin from non-selective GHRP compounds and makes it a useful tool for isolating ghrelin receptor function in experimental designs. The synthetic pentapeptide structure allows production through solid-phase synthesis with high purity requirements.
How Sermorelin differs from native GHRH
Sermorelin is a synthetic 29-amino acid peptide representing the biologically active fragment of human GHRH. The sequence corresponds to GHRH(1-29) with acetic acid modification — Tyr-Ala-Asp-Ala-Ile-Phe-Thr-Asn-Ser-Tyr-Arg-Lys-Val-Leu-Gly-Gln-Leu-Ser-Ala-Arg-Lys-Leu-Leu-Gln-Asp-Ile-Met-Ser-Arg-NH2. Published studies establish molecular weight of 3357.9 g/mol for the acetate salt (PMID: 8421207).
The peptide is identical to the first 29 amino acids of native GHRH(1-44)OH, which contains the full biological activity. Published structure-activity studies demonstrate that residues beyond position 29 in native GHRH contribute primarily to metabolic stability rather than receptor binding or activation. Sermorelin retains the native GHRH(1-29) sequence without the modifications found in analogs like CJC-1295. Published receptor binding studies confirm that Sermorelin activates GHRH receptors through the same Gs-protein coupled mechanism as native GHRH, stimulating adenylate cyclase and increasing cAMP in pituitary cell cultures.
Tesamorelin structural modifications
Tesamorelin is a GHRH analog with specific structural modifications that enhance metabolic stability. The sequence corresponds to GHRH(1-44) with a trans-3-hexenoyl group attached to the tyrosine at position 1. Published research details the 44-amino acid sequence with molecular weight 5135.9 g/mol (PMID: 19928588).
The hexenoyl modification provides lipophilicity that reduces renal clearance and proteolytic degradation compared to native GHRH. Unlike CJC-1295 which modifies the peptide sequence, Tesamorelin attaches a moiety to the native sequence — a different approach to achieving extended half-life. Published pharmacokinetic studies demonstrate that this modification extends half-life while maintaining receptor binding affinity and GHRH receptor selectivity. Published binding studies confirm that Tesamorelin activates GHRH receptors through Gs-protein coupling, stimulating adenylate cyclase with similar potency to native GHRH. Research applications use Tesamorelin for investigating sustained GHRH receptor activation.
Comparative specifications
| Feature | CJC-1295 NO DAC (Mod GRF 1-29) | CJC-1295 DAC | Ipamorelin | Sermorelin | Tesamorelin |
|---|---|---|---|---|---|
| Amino Acids | 29 | 29 | 5 | 29 | 44 |
| Molecular Weight | 3367.9 Da | 3647.4 Da | 711.9 Da | 3357.9 Da | 5135.9 Da |
| CAS Number | Mod GRF 1-29 | 863288-34-0 | 170851-70-4 | 86168-78-7 | 218949-48-5 |
| Receptor | GHRH-R | GHRH-R | GHS-R1a | GHRH-R | GHRH-R |
| Selectivity | GHRH selective | GHRH selective | GH selective | GHRH selective | GHRH selective |
| Key Modification | Sequence substitutions | DAC albumin binding | D-amino acids | Native sequence | Hexenoyl group |
| Mechanism | cAMP/PKA | cAMP/PKA | PLC/Ca2+ | cAMP/PKA | cAMP/PKA |
| Primary PMID | 15775957 | 16452336 | 10698741 | 8421207 | 19928588 |
FAQ
What concentration is used for GHRH receptor research?
Published in vitro studies typically use 1–100 nM concentrations for GHRH receptor activation in pituitary cell cultures. Higher concentrations (100–1000 nM) may be used for receptor internalization or binding studies. Verify receptor expression in your cell model.
Do GH secretagogues require GHRH for activity?
Published research demonstrates that GH secretagogues including Ipamorelin stimulate GH release in the absence of GHRH, though synergistic effects may occur with combined administration. Ghrelin receptor agonists act through distinct mechanisms from GHRH analogs.
What cell lines express GHRH receptors?
Published studies use primary pituitary cells, AtT-20 pituitary tumor cells, and HEK293 cells transfected with GHRH receptors. Verify receptor expression through binding assays or qPCR before experimental use (PMID: 15775957).
How stable are these peptides in culture media?
Peptide stability varies by structure and media composition. Published studies typically use fresh preparations or include protease inhibitors. CJC-1295 analogs with modifications show enhanced stability compared to native sequences (PMID: 16452336).
Can these peptides be used in combination?
Published research demonstrates that GH secretagogues and GHRH analogs can be combined, with potential synergistic effects on GH release. Design experiments with appropriate controls to isolate individual compound effects.
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