Scientists managed to pull out the receptor that GHRP‑6 and similar compounds bind to from pig pituitary tissue and study it in isolation. They measured how tightly the drug sticks to the receptor and found it’s a very high‑affinity interaction, similar to what’s seen in whole tissue. This basic work sets the stage for deeper molecular studies, but doesn’t change how you would currently use GHRP‑6.

The discovery of a potential new GH therapy by small molecules that induce GH secretion (GHRP-6, L-692,429, MK-0677), has increased the interest in these GH secretagogues and their receptor and mechanism of action, which is different from the one of GHRH. We report the solubilization of the GH-secretagogue-receptor-ligand-G-protein complex (apparent molecular mass of approximately 255 kDa) from porcine anterior pituitary membranes using digitonin, after labelling the receptor with [35S]MK-0677. The solubilized receptor showed high affinity (KD = 122.2 +/- 14.4 pM) and low capacity (Bmax = 3.8 +/- 0.9 fmol/mg protein). These values and the inhibition constants (Ki) for a series of GH secretagogues were similar to the values determined in membranes isolated from porcine anterior pituitary gland. The solubilization of the GH secretagogue receptor opens up the possibility for further molecular characterization and sequencing of the receptor protein, necessary step prior to the identification of the natural ligand that would act as a GHRH amplifying hormone, and that the GH secretagogues would mimic.