Summary
We have investigated the effects on platelet function of a physiologic shear stress.
The aggregation to thrombin and collagen, the release reaction [(14C) serotonin] and the procoagulant activity of washed platelet suspensions were assayed
on samples undergoing laminar oscillatory flow for 20 minutes at 37° C in polyethylene
tubes, and on paired samples kept at rest. The pulse rate was established at 72 cycles
per minute and the shear stress at the wall estimated at 26.2 dynes/cm2. The platelet suspensions were prepared at 37°C from blood samples of 15 healthy
volunteers and 15 patients with the diagnosis of coronary artery disease proven by
angiography. Our results show enhancement of platelet aggregation in samples undergoing
oscillatory flow. Furthermore, platelets from coronary patients gained additional
procoagulant activity. However, no change was encountered in the rate and speed of
the release reaction. It is concluded that exposure to a high shear stress within
an oscillatory flow system enhances platelet reactivity; this reaction may take part
in the production of platelet and coagulation changes seen in the atherosclerotic
patient and after strenuous physical exercise.
