Inositol phosphates and diacylglycerols are generated from phosphatidyl inositols by phospholipase C. They are involved in cellular calcium ion movements as second messengers. Inositol-1,4,5-triphosphate(Ins(1,4,5)P3) is an extremely important messenger that triggers calcium ion release from endoplasmic and sarcoplasmic reticulum. It is thought to increase the calcium sensitivity of the inositol- induced calcium release(IICR) channel in the intracellular calcium source. Thus, the IICR channel can be opened with a low level of calcium ion concentration, causing a dramatic calcium burst into the cytosol. The released calcium ions and diacylglycerol then activate protein kinase C, which is one of the key enzymes in signal transduction.