Shear stress-induced pH increase in plasma is mediated by a decrease in P(CO(2)): the increase in pH enhances shear...

Area of Science:

• Biophysics
• Hematology
• Biochemistry

Background:

• Shear stress is crucial for platelet activation.
• Previous studies noted pH increase in platelet-rich plasma under shear, but the mechanism was unclear.
• Cone-plate and Couette viscometers are standard tools for studying shear stress effects.

Purpose of the Study:

• To investigate if shear stress alone, using a cone-plate viscometer, increases cell-free plasma pH.
• To elucidate the mechanism of shear-induced pH increase by measuring total CO2 (TCO2) and CO2 tension (PCO2).
• To assess the impact of shear-induced pH changes on platelet activation markers, specifically P-selectin expression.

Main Methods:

• Human plasma was subjected to shearing using a cone-plate viscometer.
• Measurements included pH, TCO2, and PCO2.
• Platelet activation was assessed by monitoring P-selectin expression and aggregation under varying shear conditions and pH levels.

Main Results:

• Shearing human plasma with a cone-plate viscometer caused a time- and shear rate-dependent increase in pH.
• This pH increase correlated with a decrease in PCO2, while TCO2 remained unaffected, indicating CO2 release.
• Shear-induced P-selectin expression on platelets increased with rising pH, although aggregation was not affected.

Conclusions:

• Shear stress in a cone-plate viscometer induces plasma pH increase via PCO2 reduction.
• This shear-induced pH elevation can enhance platelet activation, specifically P-selectin expression.
• Findings suggest that pH changes in bicarbonate-containing buffers may influence results in platelet shear stress studies.