Evaluation of erythrocyte membrane oxidation due to their exposure to shear flow generated by extracorporeal blood pump.

Several similarities have been found between shear stress-induced erythrocyte damage and physiological aging of erythrocytes in terms of elevated mechanical fragility, increased erythrocyte aggregation, and decreased membrane surface charge. Accordingly, we hypothesized that blood pump circulation, which generates shear stress, would accelerate erythrocyte aging, manifesting as oxidation. Therefore, the purpose of this study was to investigate the effect of blood pump circulation on erythrocyte oxidation. Fresh porcine blood was acquired from a slaughterhouse and anticoagulated with sodium citrate. About 500 mL of anticoagulated whole blood was circulated for 180 min in an in vitro test circuit comprising a BP-80 blood pump with a pump speed and a pump pressure head of 100-120 mmHg. A blood sample was taken at the start of the circulation and 180 min afterward. The hemolysis level and oxidation amount of the erythrocyte membrane were analyzed and compared between samples. Hemolysis increased with the prolongation of shear exposure inside the pump circuit. After 180 min of blood pumping in circuit, the oxidation level of the erythrocyte membrane showed an increase of 0.1 nmol/mg protein. Moreover, the membrane oxidation levels of sheared erythrocytes were greater than those of control erythrocytes. These results suggest that blood pump circulation accelerates erythrocyte aging and give us a greater understanding of the effects of blood pump perfusion.

The shear rate promotes pinocytosis of extracellular dextran in platelets.

BACKGROUND: Several conventional studies focused on platelet pinocytosis for possible utilization as drug delivery systems. Although platelet pinocytosis is important in such utilization, the impact of the shear rate on pinocytosis is unclear. OBJECTIVE: Our objective was to investigate the relationship between shear rate and platelet pinocytosis in vitro. In addition, this study addressed the change in platelet aggregation reactivity with adenosine diphosphate (ADP) stimulation after pinocytosis. METHOD: Porcine platelet-rich plasma was mixed with fluorescein isothiocyanate (FITC)-conjugated dextran and incubated for 15 min under shear conditions of 0, 500, and 1500 s-1. After incubation, confocal microscopic scanning and three-dimensional rendering were performed to confirm the internalization of FITC-dextran into platelets. The amount of FITC-dextran accumulated via platelet pinocytosis was compared using flow cytometry at each shear rate. In addition, light transmission aggregometry by ADP stimulation was applied to platelets after pinocytosis. RESULTS: The amount of intracellular FITC-dextran increased with higher shear rates. Platelets with increased amounts of intracellular FITC-dextran did not show changes in the aggregation reactivity to ADP. CONCLUSIONS: A higher shear rate promotes platelet pinocytosis, but enhanced pinocytosis does not affect aggregation sensitivity, which is stimulated by ADP.