The Influence Of Red Cell Size On Platelet-Vessel Wall Interaction

Abstract

The hematocrit is one of the main factors influencing platelet adherence to the vessel wall. Raising the hematocrit causes an increase on platelet accumulation of about one order of magnitude.These studies disregard the influence of the red cell size. We have studied this effect using an annular perfusion chamber according to Baumgartner, with human umbilical arteries and a steady flow system. Perfusions were performed with reconstituted blood consisting of the appropriate washed red cells, aspirin treated and 51Cr labelled human platelets and human plasma. Perfusions were at a calculated vessel wall shear rate of 800 sec-1 for 5 min at 37°C. Platelet adherence was measured by 51Cr counting and controlled by morphometry. Human, goat and rabbit red blood cells were utilized. Human red blood cells (mean cell volume 100 f1) increase platelet adherence sevenfold, as the hematocrit increases from 0 to 60%. Human erythrocyte ghosts had a similar effect. Goat erythrocytes (m.c.v. 25 f1) caused no increment in adherence in the same hematocrit range. Rabbit erythrocytes (m.c.v. 70 f1) caused an intermediate increase in adherence.These data indicate that the red cell size is of major importance for platelet adherence. They may be explained by postulating that red cell rotation is responsible for diffusivity.