The GLP-1, GIP and glucagon receptors are class B GPCRs that signal mainly through Gs and cAMP. Multi-receptor reference peptides have made comparative in-vitro pharmacology an active research field.
Core assay formats
- cAMP accumulation (HTRF, luminescence or ELISA) in recombinant cell lines
- Competition binding to determine receptor affinity
- β-arrestin recruitment for signalling bias
- Receptor internalisation imaging
Comparing multi-receptor peptides
Tirzepatide is studied as a dual GIPR/GLP-1R reference agonist, while Retatrutide is studied at GIPR, GLP-1R and GCGR. Running each receptor in parallel with a native-ligand control allows relative potency to be calculated reliably.
Practical tips
- Use low-binding plastics — lipidated peptides adsorb to surfaces.
- Include a carrier protein such as BSA in assay buffer where appropriate.
- Normalise to the native ligand's maximal response.
- Record lot numbers for every curve.
Related reagents: Tirzepatide and Retatrutide reference peptides. Each batch ships with documented HPLC purity and a Certificate of Analysis on request.
