Metabolism of inositides and the activation of platelets.

Platelet activation is associated with the active metabolism of inositide lipids. Phosphodiesteratic cleavage of phosphatidylinositol and phosphatidylinositol-4,5-bisphosphate is a consequence of receptor-coupled mechanisms. Degradation of phosphatidylinositol-4,5-biphosphate is Ca2+-insensitive while that of phosphatidylinositol requires Ca2+. The phosphodiesteratic breakdown of these inositides induces the formation of 1,2-diacylglycerol which is rapidly phosphorylated to phosphatidic acid. These biochemical changes might be related to fundamental mechanisms of amplication involved in the process of platelet activation. Phosphatidic acid constitutes an ubiquitous marker for the action of a wide variety of platelet stimuli.