Efecto del cizallamiento y del difosfato de adenosina sobre la activación plaquetaria y la formación de microagregados en controles sanos. Valoración mediante citometría de flujo

Abstract

Introduction Several studies show that high shear rate cause platelet activation. But the behaviour of these activated platelets by shear and subsequent stimulus by, for example, ADP is not well established. This paper investigates an in vitro model of blood flow conditions in non-stenotic arteries. Material and methods Platelet activation is studied by flow cytometry. The shear is induced in a cone-plate viscometer at 230 s −1 that mimics the blood flow conditions in healthy arteries. CD62 and GpIIb/IIIa in their active form are selected as platelet activation markers, as well as for the formation of platelet microaggregates (MAP). The percentage of spontaneously activated platelets and the number of MAP are determined. The percentage of activated platelets and MAP after stimulating with ADP is then evaluated. In parallel, the same procedure is followed, but after previously subjecting blood samples to a shear for 5 min. In these sheared samples the percentage of activated platelets and MAP also are measured before and after stimulating with ADP. Results Shearing, as well as ADP, increases the percentage of activated platelets in whole blood. When the platelets are subsequently subjected to ADP, the percentage of activated platelets is significantly lower than when the ADP directly stimulates platelets without shearing. Conclusions Platelets subjected to shearing become refractory when they are subsequently activated by action of a physiological agonist such as ADP. However the platelets that are not sheared respond appropriately to this agonist. This refractory response in vitro may represent a cellular defence mechanism to prevent a greater degree of in vivo activation-aggregation when platelets are faced with an agonist in areas where the shear rate increases in the blood flow.