ADP Release from Red Cells Subjected to High Shear Stresses

Abstract

The deposition of thrombotic material (primarily platelets) upon the surfaces of natural but damaged surfaces (e.g. BAUMGARTNER et al.), as well as onto any artificial surfaces (e.g. LEONARD et al., GRABOWSKI et al.) requires continuous blood flow rather than blood “stasis”. For the simple reason that the material to be deposited comprises only a few percent of the volume of the blood, it can thus be only derived from a very much larger volume of blood than a volume of a deposit. This absolute flow requirement makes it necessary to reconsider many current biochemical theories about the mechanisms governing thrombotic processes — since the“essential” blood stream not only supplies the reaction partners but also carries away activating species (e.g. released mediators, activated enzymes, as elaborated elsewhere: SCHMID-SCHÖNBEIN 1977). This notwithstanding, it is well established that thrombotic processes are much enhanced by rapid flow, especially in the presence of red cells. The reason for the enhancement of platelet “reactivity” in the presence of flowing red cells has not been established. Applying mass transport principles customary in engineering sciences, BLACKSHEAR et al., LEONARD et al. And TURRITO et al. have often explained the phenomenon by the assumption of an enhanced “platelet diffusivity” (diffusion coefficient), i.e. an acceleration of spontaneous platelet motions towards the vessel wall by directed convective motion induced by “swirling” red cells that “mix” the platelets and move them towards the thrombotic deposit. In life sciences (see textbook of General Physiology), and especially in circulatory physiology,a more strict differentiation between processes governed by diffusion (motion of dissolved species along a concentration gradient) and convection (motion of the solute or continuous phase) is customary. GOLDSMITH et al. have therefore recently used the term“radial dispersion coefficients”.

Supported by Sonderforschungsbereich 109 (Künstliche Organe) of the Deutsche Forschungsgemeinschaft at RWTH Aachen, Project C₂

Supported by Thyssen Foundation, Cologne

In partial fulfillment of the requirements of a doctoral dissertation (RWTH Aachen)