Effects of nitric oxide on platelet activation during plateletpheresis and in vivo tracking of biotinylated platelets in humans.

Background: The use of platelet transfusions has risen considerably over the last few years, which leads to the collection and transfusion of a greater number of donor plateletpheresis units. Plateletpheresis activates platelets in platelet concentrates, which determines the degree of the storage lesion subsequently observed.

Study Design And Methods: As nitric oxide (NO) is a potent inhibitor of platelet aggregation and activation, a placebo-controlled crossover trial was performed in healthy young male volunteers to determine whether the NO-donating compound, sodium nitroprusside (SNP), decreases platelet activation during apheresis and whether activated (p-selectin+) platelets circulate in vivo after transfusion. The study also investigated whether nonradioactive biotin labeling of apheresis platelets is feasible for the study of platelet recovery after transfusion in humans.

Results: Platelet activation increased after plateletpheresis in the platelet components, but SNP did not inhibit platelet activation during apheresis, as measured by the percentage of p-selectin expression and the secretion of soluble p-selectin and RANTES. Only a minor increase in p-selectin+ platelets was seen in peripheral blood at 60 minutes after transfusion of the platelets, a rise that was considerably less than that calculated in p-selectin+ platelets if they all were recovered as activated platelets after transfusion. Biotin-labeled platelets averaged 1.5 percent at 10 minutes after transfusion and increased slowly to 2.6 and 3.4 percent after 60 minutes and 24 hours, respectively (p<0.05).

Conclusion: SNP does not decrease platelet activation during apheresis and subsequent storage, and only a minor proportion of activated (p-selectin+) platelets circulate after transfusion in men. Moreover, biotin labeling of PCs can safely be used in humans for the study of platelet recovery after transfusion, and measuring recovery at 1 hour may lead to an underestimation of the true recovery when activated platelets are transfused.