[Determination of phosphatidylinositol turnover for pharmacological analysis]

The most popular method for determining phosphoinositide hydrolysis is the analysis of water-soluble materials in cells or tissues that have been labeled with [3H]inositol by separating them on anion exchange open columns or HPLC columns. Recently, a radioreceptor assay has become available for the analysis of inositol 1,4,5-trisphosphate (IP3) using IP3 receptors and [3H]IP3; this allows the analysis of IP3 in vivo. On the other hand, radiolabeled phosphoinositides are measured by thin layer chromatography to analyze the breakdown or synthesis of phosphoinositide in response to stimuli. The purified enzyme with phospholipid vesicles can be used to hydrolyze [3H]phosphatidylinositol 4,5-bisphosphate (PIP2) to [3H]IP3, which makes it possible to search for direct action of a drug on phospholipase C.