Activation of human platelets by ADP causes a rapid rise in cytosolic free calcium without hydrolysis of phosphatidylinositol-4,5-bisphosphate.
Phosphatidylinositol-4,5-bisphosphate decreased 40% within 10 seconds after the addition of thrombin to platelets. This thrombin-induced loss was accompanied by a corresponding increase of inositol phosphates. In contrast, within the first 60 seconds after exposure of platelets to ADP there was no detectable change in the amounts of phosphatidylinositol-4,5-bisphosphate or inositol phosphates. Both thrombin and ADP, however, caused a very rapid rise of cytosolic free calcium, as measured by Quin-2. The magnitude of this rise of calcium was similar for the two agonists. These results suggest that in platelets, agonist stimulation may lead to increased cytosolic free calcium independently of phosphatidylinositol-4,5-bisphosphate degradation.
Fisher
G J
GJ
Bakshian
S
S
Baldassare
J J
JJ
D000244:Adenosine Diphosphate / Q000494:pharmacology*; D000634:Aminoquinolines; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D007294:Inositol / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D010974:Platelet Aggregation / Q000187:drug effects*; D013917:Thrombin / Q000494:pharmacology; D013997:Time Factors
D000634:Aminoquinolines; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D010743:Phospholipids; D007294:Inositol; D000244:Adenosine Diphosphate; D013917:Thrombin; C035739:Quin2; D002118:Calcium