Time-dependent effects of EPO treatment on platelet reactivity in whole blood as measured by P-selectin–positive and CD63-positive platelets in response to stimulation with thrombin receptor–activating peptide (TRAP).

Two doses of TRAP were used: 3.7 μmol/L and 7.3 μmol/L, which elicited approximately 20% and 50%, respectively, of the maximal stimulation at baseline. Healthy male volunteers (n = 30) received bolus infusions of either 500 U/kg of EPO (black squares; n = 10), 100 U/kg of EPO (open triangles; n = 10), or placebo (open circles; n = 10). EPO did not affect platelet reactivity 1 hour after infusion (symbols adjacent to baseline values) but maximally increased platelet reactivity after 9 days (ie, in a period similar in length to platelet life time). Data are mean ± SEM.