Platelet interaction with subendothelium in a perfusion system: Physical role of red blood cells

Subendothelium from everted rabbit aorta was exposed in an annular perfusion chamber to whole blood and platelet rich plasma under controlled flow conditions. Platelet rich plasma was perfused in the in vitro system for periods as long as 100 min without altering the ability of the platelets to adhere to subendothelium. The rate of platelet deposition obtained from whole blood was approximately 57 times that from platelet rich plasma. Deposition results were compared with predictions obtained from mass transport theory. The analysis indicated that the increase in deposition caused by red cells was consistent with a physical, rather than humoral, mechanism-red cell motions in flowing blood increase platelet diffusivity by two orders of magnitude over that in plasma. The possibility of a minor humoral role for the red cells could not be entirely excluded.