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[Relation between the changes in Na+/H+-exchange and cytoplasmic Ca levels in platelet activation]
Biulleten' Eksperimental'Noi Biologii I Meditsiny
|September 1, 1988
Summary
Platelet activation involves complex interactions between intracellular pH and calcium levels. Findings reveal that sodium-hydrogen exchange and calcium influx are mutually dependent, influencing platelet responses to agonists like PAF and thrombin.
Area of Science:
- Biochemistry
- Cell Biology
- Hematology
Background:
- Platelet activation is crucial for hemostasis and thrombosis.
- Cytoplasmic pH (pHi) and intracellular calcium ([Ca2+]) dynamics are key regulators of platelet function.
Purpose of the Study:
- To investigate the interplay between pHi changes and Ca2+ concentration in human and rat platelets.
- To elucidate the role of Na+/H+ exchange in agonist-induced platelet responses.
Main Methods:
- Utilized fluorescent probes BCECF and quin-2 to monitor pHi and [Ca2+] respectively.
- Experimentally manipulated extracellular Na+ and Ca2+ concentrations.
- Applied agonists such as platelet-activating factor (PAF) and thrombin, and Ca-ionophore A23187.
Main Results:
- Inhibition of Na+/H+ exchange reduced Ca2+ signals induced by PAF and thrombin.
- Both PAF and thrombin caused an initial decrease followed by an increase in pHi, with thrombin eliciting a more pronounced increase.
- Extracellular Ca2+ removal and Ni2+ addition suppressed pHi increase, while Ca-ionophore A23187 induced a pHi rise, dependent on extracellular Ca2+.
Conclusions:
- A mutual interdependence exists between Ca2+ influx and pHi changes in platelets.
- Ca2+ influx enhances agonist-mediated Na+/H+ exchange activation.
- Na+/H+ exchange activation, in turn, potentiates stimulus-induced Ca2+ influx, highlighting a positive feedback loop in platelet activation.