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Second messenger function of phosphatidic acid in platelet activation.
M H Kroll1, G B Zavoico, A I Schafer
1Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115.
Journal of Cellular Physiology
|June 1, 1989
Summary
1-stearoyl-2-arachidonoyl phosphatidic acid (SAPA) triggers platelet aggregation and enhances thrombin-induced responses. SAPA acts as a positive feedback signal, amplifying platelet activation pathways.
Area of Science:
- Biochemistry
- Cell Biology
- Hematology
Background:
- Phosphatidic acid (PA) is synthesized in response to platelet agonists.
- The precise function of PA in platelet signaling remains largely uncharacterized.
Purpose of the Study:
- To investigate the role of 1-stearoyl-2-arachidonoyl phosphatidic acid (SAPA), a major human platelet PA species, in platelet activation.
- To elucidate the signaling mechanisms by which SAPA influences platelet function.
Main Methods:
- Platelet aggregation assays
- Measurement of intracellular calcium mobilization
- Analysis of protein kinase C activation
- Assessment of arachidonic acid release and thromboxane A2 production
- Pharmacological inhibition studies using indomethacin
Main Results:
- SAPA induces platelet aggregation independently.
- SAPA pretreatment potentiates thrombin-induced platelet aggregation and secretion.
- SAPA stimulates phosphatidylinositol-4,5-bisphosphate (PIP2) breakdown, diacylglycerol generation, and intracellular calcium release.
- SAPA promotes arachidonic acid release and thromboxane A2 synthesis.
- SAPA-induced platelet activation is dependent on cyclooxygenase products.
Conclusions:
- SAPA functions as a potent endogenous activator of human platelets.
- SAPA may amplify receptor-mediated signaling by activating PIP2-specific phospholipase C.
- These findings highlight SAPA's critical role in positive feedback loops during platelet activation.