Created by Department of Biology, Davidson College, Davidson, NC 28036
More information about inositol trisphosphate from the WIkipedia article about IP3 :
Inositol trisphosphate or inositol 1,4,5-trisphosphate (also commonly known as triphosphoinositol; abbreviated InsP3 or IP3), together with diacylglycerol, is a secondary messenger molecule used in signal transduction in biological cells. It is made by hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2), a phospholipid that is located in the plasma membrane, by phospholipase C.
IP3 binds to and activates the InsP3 receptor on the membrane of the endoplasmic reticulum (ER), and sarcoplasmic reticulum (SR) opens a calcium channel, resulting in the release of Ca2+ into the cytoplasm, and sarcoplasm respectively.This increase in Ca2+ activates the ryanodine receptor-operated channel on the SR, leading to a further increase in the Ca2+.