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Changes of platelet functions by extracellular sodium ion
Y Ishikawa1, A Ogawa, S Sasakawa
1Japanese Red Cross Central Blood Center, Tokyo.
Thrombosis Research
|February 1, 1991
Summary
Extracellular sodium (Na+) significantly impacts platelet function. Removing Na+ alters responses to thrombin and other agonists, indicating Na+ has direct effects beyond the Na+/H+ exchanger.
Area of Science:
- Biochemistry
- Hematology
- Cellular Physiology
Background:
- Platelets play a crucial role in hemostasis and thrombosis.
- Extracellular ion concentrations can modulate cellular signaling and function.
- The role of extracellular sodium (Na+) in platelet activation is not fully understood.
Purpose of the Study:
- To investigate the specific effects of extracellular Na+ on various platelet responses.
- To determine if Na+ influences platelet activation through the Na+/H+ exchanger or other mechanisms.
Main Methods:
- Platelet aggregation and serotonin release assays were performed in both Na+-containing and Na+-free buffers.
- Stimulation was induced using thrombin, TPA, and arachidonic acid (AA).
- The effect of adding NaCl to Na+-free buffer and the influence of indomethacin were assessed.
Main Results:
- Cytoplasmic pH decreased upon stimulation with thrombin, TPA, and AA, irrespective of Na+ presence.
- Thrombin-induced platelet aggregation and serotonin release were higher in the presence of Na+.
- TPA- and A23187-induced responses were reduced in Na+-free conditions.
- Platelet aggregation in Na+-free buffer was restored by NaCl addition.
- Indomethacin's inhibition of thrombin-induced aggregation was less potent than Na+ removal.
Conclusions:
- Extracellular Na+ directly influences platelet responses, independent of Na+/H+ exchange inhibition.
- Sodium ions affect platelet activation mechanisms distinct from arachidonic acid mobilization.
- These findings highlight a direct role for Na+ in regulating platelet function.