Phosphoinositidase C Activation Assay III: HPLC Analysis of Cellular Phosphoinositides and Phosphoinositols

In Chapters 1 and 2 , the extraction procedures for recovery of the phosphoinositols and phosphoinositides from cells in suspension or culture are described, together with simple separation procedures to resolve them into their general classes (InsP₁ , InsP₂ , and so on, and PtdIns, PtdInsP, and PtdInsP₂ ). However, in reality, the metabolism of the phosphoinositols is complex (1 ) leading to the formation of several isomeric forms in each class. Furthermore, since the discovery of a phosphoinositide 3-kinase (in addition to the previously known 4-and 5-kinases) (2 ), it is clear that the phosphoinositides also exist in different isomeric forms.