Changes in cytoplasmic pH and in membrane potential in thrombin-stimulated human platelets

Area of Science:

• Biochemistry
• Hematology
• Cell Biology

Background:

• Platelet activation by thrombin is a complex process involving sequential membrane and intracellular events.
• Previous studies indicated rapid membrane depolarization as an early response to thrombin.
• The role of transmembrane pH changes in early platelet activation remained less understood.

Purpose of the Study:

• To investigate the changes in human platelet transmembrane pH gradient upon thrombin stimulation.
• To correlate pH gradient changes with other early platelet activation events like membrane potential and serotonin secretion.

Main Methods:

• Adaptation of intracellular pH measurement techniques using weak bases and fluorescein derivatives.
• Measurement of transmembrane pH gradient using lipophilic cations for membrane potential assessment.
• Quantification of thrombin dose-dependency and time-course of pH changes.

Main Results:

• Thrombin stimulation induces a rapid and significant change in the human platelet transmembrane pH gradient.
• The observed pH gradient changes are both time-dependent and thrombin dose-dependent.
• These pH dynamics closely parallel the changes in membrane potential and serotonin secretion.

Conclusions:

• Transmembrane pH gradient alteration is an early, rapid, and integral component of thrombin-induced human platelet activation.
• This pH change is a key event that parallels membrane potential shifts and serotonin release.
• The findings provide new insights into the early biochemical cascade of platelet response.