GCG and pancreatic insulinoma: Ramos et al. demonstrated in the insulinoma cell line INS-1E that while the gut-derived incretin, glucagon-like peptide-1 (GLP-1), induced a rapid increase of intracellular cAMP via G protein-coupled receptor (GPCR) and tmAC, a direct glucose stimulus (16 mM) results in a delayed (detectable at least after 5 min) calcium-dependent rise of cAMP for which sAC is responsible (Ramos et al., 2008).