Platelet Activation in Response to Phlebotomy

ABSTRACT. Plasma concentrations of β-thromboglobulin (BTG) and platelet factor 4 (PF4) were measured in three consecutive blood samples from 29 healthy male blood donors. The first sample was collected after 15 min of rest, the second immediately after a phlebotomy of 450 ml blood and the third after a further 15 min of rest. The mean baseline plasma BTG and PF4 values were 68 × 5 and 13.8 ± 0.7 ng/ml, respectively. The second sample's mean plasma values of these two platelet-specific proteins were significantly higher (88 ± 9 and 24.1 ± 4.1 ng/ml, respectively). The plasma concentrations of BTG and PF4 in the last sample, however, had returned to baseline levels. It is concluded that significant but short-lasting platelet activation and secretion take place in healthy subjects in response to an acute but comparatively mild blood loss even though the platelets do not participate in the process of hemostasia.