The rapid polyphosphoinositide metabolism may be a triggering event for thrombin-mediated stimulation of human platelets.
The metabolism of polyphosphoinositides was examined in human platelets activated by thrombin. The addition of thrombin to [3H]glycerol-labeled platelets induced an initial loss and a subsequent increase of the radioactivity in phosphatidylinositol-4,5-bisphosphate (TPI) without any significant change in phosphatidylinositol-4-phosphate (DPI). A marked enhancement of [32P]Pi incorporation into TPI occurred in parallel with an increase in this lipid content, which was accompanied with a conccurent decrease in phosphatidylinositol (PI). The rate of this subsequent increase in TPI was smaller than that observed in [3H]arachidonic acid-labeled platelets, suggesting that formed TPI in activated platelets may contain much greater amount of arachidonate than preexisting TPI in resting platelets. These data indicate that thrombin causes a rapid change in TPI metabolism (initial degradation of preexisting TPI and subsequent production of arachidonate-rich TPI), which might be a primary candidate to modulate thrombin-induced function in human platelets.
D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000097:blood; D001792:Blood Platelets / Q000502:physiology*; D005990:Glycerol / Q000097:blood; D006801:Humans; D007700:Kinetics; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols / Q000097:blood*; D010761:Phosphorus Radioisotopes; D010974:Platelet Aggregation; D013917:Thrombin / Q000502:physiology*
D001095:Arachidonic Acids; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D010761:Phosphorus Radioisotopes; D016718:Arachidonic Acid; D013917:Thrombin; D005990:Glycerol