METABOLIC PROPERTIES OF HUMAN PLATELET MEMBRANES .2. THROMBIN-INDUCED PHOSPHORYLATION OF MEMBRANE LIPIDS AND DEMONSTRATION OF PHOSPHORYLATING ENZYMES IN PLATELET MEMBRANE

  • 1 January 1976
    • journal article
    • research article
    • Vol. 35  (2) , 364-376
Abstract
Washed human platelets were labeled with either 32Pi or glycerol-1-14C and the distribution of the label in the phospholipids determined. 32Pi was introduced primarily into polyphosphoinositides, i.e., di- and triphosphoinositide but the label from glycerol which indicated de novo synthesis of lipid molecules, did not appear in these phospholipids. In the course of thrombin-induced aggregation and release, the phosphate incorporation into phosphatic acid, di- and triphosphoinositide was rapidly stimulated in parallel to the platelet reaction. The incorporation of glycerol did not change under the same conditions. Phosphoinositides with rapid incorporation of phosphate groups were apparently not as rapidly synthesized de novo and presumably formed a separate phospholipid pool in the platelets. Only the phosphorylating reactions were stimulated by the thrombin aggregation. The necessary enzymes for these reactions, i.e., diglyceride kinase, phosphatidylinositol kinase, and phosphatidylinositol-phosphate kinase all were associated with a well characterized platelet membrane fraction.