Ins(1,2)P2 (sodiumsalt) is one of the many inositol phosphate (InsP) isomers that could act as small, soluble second messengers in the transmission of cellular signals. The most studied InsP Ins(1,4,5)P3, is a second messenger produced in cells by phospholipase C (PLC)-mediated hydrolysis of phosphatidylinositol-4,5-biphosphate. Binding of Ins(1,4,5)P3 to its receptor on the endoplasmic reticulum results in opening of the calcium channels and an increase in intracellular calcium. Ins(1,2)P2 (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.