Prevention of acquired defects in platelet function during blood processing.

Two kinds of platelet concentrates were prepared in this study: one as pelleted platelets from platelet-rich plasma (PCs), and the other as a platelet suspension from the buffy coat fraction (nonpelleted PCs). The characteristics of both platelet concentrates were studied. White cell contamination in the nonpelleted PCs was below the threshold of detection by a microcell counter (less than 300 cells/microliter of concentrate); in the pelleted PCs, it was 3 +/- 1 x 10(7) cells per concentrate. The difference between the white cell contamination in pelleted PCs and nonpelleted PCs was significant (p less than 0.001). The degree of aggregation induced in pelleted PCs by ADP (9 microM) and collagen decreased to 33 and 55 percent, respectively, of that in platelet-rich plasma. The secondary wave of platelet aggregation induced by ADP and epinephrine was absent in pelleted PCs, and ATP secretion from these platelets by ADP stimulation also decreased remarkably. However, the degrees of aggregation and ATP secretion in nonpelleted PCs were similar to those in platelet-rich plasma. Furthermore, it was found that the amount of platelet factor 4 release seen in pelleted PCs was large in comparison to that in nonpelleted PCs and platelet-rich plasma. These results suggested that the deterioration of platelet function might have resulted from the platelet activation induced by pellet formation during the preparation of PCs from platelet-rich plasma.