THE EXPRESSION OF P-SELECTIN DURING COLLECTION, PROCESSING, AND STORAGE OF PLATELET CONCENTRATES - RELATIONSHIP TO LOSS OF IN-VIVO VIABILITY

BACKGROUND: Recent studies suggested that platelet activation with sur face expression of p-selectin on stored platelets may be related to a loss of viability. At present, there has been no thorough investigatio n of the extent or significance of p-selectin expression during the co llection, processing, and storage of platelet concentrates (PCs) under various conditions. STUDY DESIGN AND METHODS: Platelet surface expres sion of p-selectin (CD62) was determined on fixed platelet samples usi ng fluorescein-conjugated monoclonal antibodies. Platelet viability wa s assessed by autologous transfusion of platelets stored for 5 days an d labeled with either Cr-51 or In-111. RESULTS: Little (2-10%) platele t expression of p-selectin was found in whole blood and platelet-rich- plasma preparations, whereas PCs showed a substantial increase in p-se lectin expression to levels of 20 to 30 percent. Both fresh PCs and th ose stored for 5 days, obtained with one cell separator(MCS, Haemoneti cs) showed substantially lower levels of p-selectin expression than PC s from two other cell separators (Spectra, COBE, and CS-3000 with TNX- 6, Baxter Healthcare). Exposure of platelets to EDTA, cold, or a pH be low 6.2, conditions that are known to result in the loss of viability upon transfusion, produced substantial and irreversible p-selectin exp ression. PCs with a pH of 6.2 to 6.8 (conditions in which no loss of v iability has been demonstrated) also showed pronounced p-selectin expr ession, which returned to control values after incubation at 37 degree s C in plasma at pH 7.0 to 7.2. With storage under current conditions, the in vivo studies (n = 61) demonstrated a rather poor correlation b etween p-selectin expression and the percentage of recovery (r = -0.25 ) but a somewhat better correlation with survival (r = -0.42). Better correlations were observed with the extent of shape change, lactate, a nd hypotonic shock response. CONCLUSION: These studies show that p-sel ectin expression on the platelet surface is a predictor of platelet vi ability, although the extent of shape change and the hypotonic shock r esponse may be more sensitive.