cAMP is one of the most important s

cAMP is one of the most important second messengers involved in a variety of physiological responses and is thus widely measured in HTS. Present methods for cAMP measurement include fluorescence polarization (FP)19, HitHunter EFC technology based on β-galactosidase activity complementation, cyclic-nucleotide-gated ion channel (CNGC) coupled cAMP assay based on membrane potential20, as well as cAMP-Glo assay developed by Promega. All of them reflect a decline of fluorescent signals in response to an increase in cAMP concentration. Other cAMP assays, based on reporter gene by splicing the reporter luciferase coding sequence under the control of Cre (causes recombination), measure elevations of cAMP levels exhibited as an increase in fluorescence/luminescence intensity. Obviously, this approach is labor intensive (requires more than 4 hours) and reflects cAMP concentration indirectly. Although cAMP measurements tend to offer more accurate and physiologically relevant results with low false positive hits, some of them require special apparatus/fittings (e.g., optical filters) and expensive regents (e.g., engineered antibodies fused with compensatory enzyme or fluorescent indicators).