Abstract 370: Supernates from Stored Red Blood Cells Inhibit Collagen-Mediated Aggregation of Platelets Exposed to Arterial Shear Rates
Background: Uncontrolled bleeding is a leading cause of death on the battlefield. We demonstrated previously that supernatant fluid from stored non-leukoreduced (NLR) red blood cells (RBC) inhibited aggregation of platelets in whole blood from healthy donors as measured by impedance aggregometry and decreased GPIIb/IIIa expression. In the current study, we examine stored NLR RBC supernatant fluid inhibition of platelet aggregation in a physiological model of arterial flow.
Methods: Fresh citrated blood (500 ul) was mixed with supernate from stored NLR RBC (median age 44 days, 250 ul) and tyrodes buffer (250 ul) for impedance aggregometry. Flow model experiments utilized blood prepared with calcein-labeled platelet rich plasma, RBCs (40% hematocrit), and supernate (25% total volume). Arterial simulated flow (shear rate 1000/sec) over collagen I was carried out in a 75μm x 350μm x 5mm microchamber (Bioflux). GPIIb/IIIa expression was assessed by flow cytometry.
Results: Supernates from nine stored NLR RBC units decreased platelet aggregation amplitude in fresh blood from eleven donors by an average of 40±12% vs Tyrode’s buffer controls while one supernate did not exhibit significant inhibition. In concordance with previously reported results, supernates decreased GPIIb/IIIa expression on platelets in whole blood by 53±1.2%. Linear regression analysis of a single flowed experiment showed a 60.5% decrease in aggregation rate (NLR RBC supernate vs HEPES buffered saline control). Inhibition of the rate of aggregation observed in the flow model vs aggregation amplitude by impedance correlated well (sup1: 85.1% vs. 52%; sup 2: 46.6% vs. 41%).
Conclusions: Stored NLR RBC units significantly inhibit collagen-stimulated aggregation of platelets in the presence of high (arterial) and low (stirring) shear rates, and reduce expression of the fibrinogen-binding glycoprotein, IIb/IIIa, on the platelet surface. The substantial decrease in platelet aggregation in a physiologically relevant model of whole blood flow suggests massive transfusion of NLR RBC units may decrease the hemostatic capacity of platelets in combat casualties and contribute to uncontrolled hemorrhage. [apc1]unclear
- © 2012 by American Heart Association, Inc.