Ins(1,4,5,6)-P4 is one of several different inositol oligophosphate isomers implicated in signal transduction. Production of Ins(1,4,5,6)-P4 by intestinal epithelial cells increases approximately 2-14 fold, depending on the strain and incubation time, following infection with Salmonella. Ins(1,4,5,6)-P4 antagonizes epidermal growth factor (EGF) signalling through the phosphatidylinositol 3-kinase pathway. Ins(1,4,5,6)-P4 (tested as the D/L racemic mixture) is ~1,000-fold less potent than Ins(1,4,5)-P3 at initiating Ca2+ release when injected into Xenopus oocytes.