A rightward shift of the agonist dose-response curve, and a decrease in the maximal response, was observed in the presence of 10-7M ZM241385. This shows that ZM241385 non-competitively antagonised (by 4- to 5-fold) the agonist-induced increase in intracellular cAMP levels.
The HitHunter® cAMP HS assay is particularly suitable for detecting small changes in cAMP levels such as those seen in the rat PC12 phaeochromocytoma cellline. Both agonist and antagonist data can be generated in conjunction with the BMG LABTECH microplate reader.
G-protein coupled receptors (GPCRs) are cell surface receptors, which represent the most predominant drug targets. Following receptor stimulation, intracellular signaling pathways are activated, which in case of a Gs receptor leads to an increase and in case of a Gi receptor to a decrease of the second messenger cAMP.
The HitHunterTM cAMP assay by DiscoverX employs competitive binding of sample cAMP and peptide-labelled cAMP that is able to complement an enzyme acceptor added to the reaction. In the presence of cAMP in the sample, antibody binding sites are occupied leading to free peptide-labelled cAMP that complements the enzyme. The completed and active ß-Galactosidase enzyme converts a substrate under emission of light.
Using a cAMP standard curve as well as PC12 cells together with a well-known agonist the PHERAstar® microplate reader proved to be highly sensitive and suitable to read the assay.