Ipamorelin

Receptor selectivity

Ipamorelin is best known in the literature as a selectivity benchmark. Comparative studies against GHRP-6 and hexarelin reported that ipamorelin stimulated growth hormone release in animal models without the parallel increases in ACTH, cortisol and prolactin that accompanied the earlier compounds. Receptor-binding panels have been used to confirm that its activity is concentrated at GHS-R1a rather than distributed across related receptors, which makes it a cleaner probe for dissecting a single pathway.

Signal transduction

GHS-R1a is a Gq-coupled receptor: activation drives phospholipase C, inositol trisphosphate generation and intracellular calcium mobilisation in somatotrophs. Cell-based assays with ipamorelin measure calcium flux, inositol phosphate accumulation and beta-arrestin recruitment, and the receptor's unusually high constitutive activity means investigators often measure agonist effects against a substantial baseline.

Combination and comparative work

• Side-by-side profiling with GHRP-2, GHRP-6 and hexarelin to map structure–selectivity relationships within the secretagogue class
• Studies of ghrelin-receptor involvement in gastric motility and feeding behaviour in rodent models

Structural chemistry

Store sealed vials of the lyophilized powder at −20 °C, shielded from light and moisture; the dry material is markedly more stable than any solution. Bring a vial to room temperature before opening so moisture does not condense on the cake. Reconstitute with bacteriostatic or sterile water added down the vial wall, and swirl gently until dissolved rather than shaking. Hold the resulting solution at 2–8 °C, label it with lot number and date, and aliquot if the work spans several sessions. Wear gloves, keep the workspace clean, and dispose of material per your institution's procedures.