GHRP-2

Origins of the GHRP class

GHRP-2 belongs to a family that began with met-enkephalin analogues found to release growth hormone through a receptor unrelated to GHRH. Systematic modification of that scaffold produced GHRP-6, then GHRP-2, and the search for the endogenous ligand of the receptor these peptides activated eventually led to the discovery of ghrelin. Much of the historical pharmacology of GHS-R1a was therefore worked out using GHRP-2 as the probe.

Signalling and potency

As a GHS-R1a agonist, GHRP-2 engages a Gq-coupled receptor that mobilises intracellular calcium through phospholipase C and inositol trisphosphate. Laboratory assays measure calcium flux, IP-1 accumulation and beta-arrestin recruitment. In comparative rankings GHRP-2 has generally been reported as more potent than GHRP-6 on a molar basis, and it is often used as the positive control when new secretagogues are screened.

Selectivity profile

• Animal studies reported concurrent increases in prolactin and cortisol alongside growth hormone, distinguishing it from the narrower profile attributed to ipamorelin
• Comparative work with hexarelin has examined cardiac CD36 binding, a target outside the classical secretagogue receptor
• Combination models with GHRH analogues test whether Gq and Gs signalling converge at the somatotroph

Structure–activity relationships

Keep sealed vials at −20 °C, protected from light and moisture, and allow the vial to reach room temperature before opening so condensation does not wet the cake. Reconstitute with bacteriostatic or sterile water introduced gently down the inner wall, then swirl until clear; the tryptophan and naphthylalanine residues make this peptide light-sensitive, so keep solutions covered or in amber vials. Store working solution at 2–8 °C, mark the lot and preparation date, and aliquot rather than repeatedly freezing and thawing. Handle with gloves and follow your laboratory's chemical hygiene and disposal rules.