Rapid platelet morphological changes visualized by scanning-electron microscopy: kinetics derived from a...

Area of Science:

• Hematology
• Cell Biology
• Biophysics

Background:

• Platelet activation is a crucial process in hemostasis and thrombosis.
• Morphological changes, including shape alteration and pseudopod formation, are key indicators of platelet activation.
• Previous methods limited the ability to capture the rapid kinetics of these events.

Purpose of the Study:

• To investigate the kinetics of platelet morphological changes upon activation using a quenched-flow technique.
• To determine the precise timing of shape alterations and bleb formation following stimulation with various agonists.
• To assess the utility of the quenched-flow approach for studying platelet function.

Main Methods:

• Utilized a quenched-flow system to rapidly mix platelets with activating agents (ADP, thrombin, A-23187, adrenalin) and then fix them.
• Employed scanning electron microscopy to visualize and quantify morphological changes in platelets at various time points (0.5 S to 10 S).
• Measured platelet resistive volume changes to correlate with morphological alterations.

Main Results:

• Significant platelet shape changes, including a decrease in disc-shaped cells and an increase in blebbed forms, were observed as early as 0.5 seconds after ADP or thrombin stimulation.
• Fully activated, multiple-blebbed forms constituted approximately 60% of platelets by 1.7 seconds.
• The calcium ionophore A-23187 induced slightly slower changes, while adrenalin was less potent.
• Platelet resistive volume increased rapidly, independent of shape variations.

Conclusions:

• The quenched-flow approach provides novel insights into the rapid kinetics of platelet activation.
• Platelet morphological changes commence significantly earlier than previously appreciated.
• This methodology offers a powerful tool for detailed studies of platelet function and dynamics.