Peptide tesamorelin is characterized in vitro by two complementary assay types: receptor-binding assays that measure affinity for the GHRH receptor, and cAMP functional assays that measure Gs-coupled signaling. This guide sets out cell systems, controls, readouts and analysis for both. The compound background is in the tesamorelin structure and in-vitro research profile.
What does a GHRH-receptor assay measure?
The GHRH receptor couples to Gs, so agonist binding activates adenylyl cyclase and raises intracellular cAMP, which activates PKA and CREB. A binding assay reports affinity (Ki or Kd); a cAMP assay reports potency (EC50) and maximal response (Emax). Running both separates a ligand that binds well from one that signals well. The receptor class distinction from ghrelin-receptor ligands is covered in GHRH analogs versus GH secretagogues.
Which cell systems are used?
- Recombinant lines: HEK293 or CHO cells stably expressing the human GHRH receptor, with the parental line as a negative control.
- Reporter lines: the same cells with a CRE-luciferase or cAMP biosensor readout.
- Primary or pituitary models: cultured pituitary cells, where growth-hormone release by ELISA is the downstream readout.
How is a binding assay designed?
Use membranes or whole cells with a labelled GHRH ligand and compete with a tesamorelin concentration series. Include non-specific binding wells with excess unlabelled ligand, fit a one-site competition model, and convert IC50 to Ki. General methods and readouts are described in the GPCR binding methods guide listed below.
How is a cAMP assay designed?
- Seed cells and starve of serum if the assay allows, to reduce peptidase activity.
- Pre-incubate with a phosphodiesterase inhibitor such as IBMX so cAMP accumulates.
- Add tesamorelin across a 10 to 12 point half-log series prepared from a calculated stock (see tesamorelin vial stock concentration math).
- Stop after a fixed short interval, lyse, and read cAMP by HTRF, luminescence or ELISA.
- Fit a four-parameter logistic curve for EC50, Emax and Hill slope.
Which controls are needed?
| Control | Purpose |
|---|---|
| Vehicle at matched solvent content | Baseline and solvent effect |
| Native GHRH(1-44) or sermorelin | Reference agonist for potency comparison |
| Forskolin | Receptor-independent maximum for adenylyl cyclase |
| GHRH-receptor antagonist | Confirms the response is receptor-mediated |
| Parental cells without receptor | Rules out off-target cAMP signal |
Two pitfalls recur. Native GHRH is degraded by dipeptidyl peptidase IV in serum-containing media, which is why the N-terminally capped analog is useful as a comparator, and a 44-residue peptide can adsorb to plastic, so use low-bind labware. The Tesamorelin listing is supplied as a lyophilized vial for these preparations.
Related research guides
Research-use note
All materials discussed are supplied for in vitro laboratory research use only, and are not for human or animal use.
