The time course of filtration test as a model for microvascular plugging by white cells and hardened red cells.

The propensity of white blood cells and rigidified red blood cells to plug narrow channels was studied in an in vitro model. Blood cell suspensions (20 ml) with a hematocrit level of 10% were pumped through Nuclepore filters with a nominal pore diameter of 5 micron at constant flow rates (0.82-6.1 ml/min), and the pressure-time curves were recorded. An initial fast rise (K1) and a later slow rise (K2) of the pressure-time curve were observed; according to earlier studies (Skalak, R., Impelluso, T., Schmalzer, E.A., and Chien, S. (1983), Biorheology 20, 41), K1 reflects the dynamic plugging-unplugging process and K2 the permanent plugging of pores by rigid cells. Changes of the flow rate had no influence on K1 (greater than or equal to 1.6 ml/min) or K2. The addition of small concentrations of mononuclear leukocytes to the red cell suspensions resulted in a dose-dependent increase in K1, but did not affect K2. Admixture of partially hardened red cells (0.03% glutaraldehyde for 30 min) with normal red cells at a constant total hematocrit caused increases of both K1 and K2. From these results we conclude that both white cells and hardened red cells tend to plug narrow channels. White cells, however, may cause less permanent plugging than rigidfied red cells. These results may help to understand microcirculatory disorders seen in sickle cell crisis or leukocytosis and leukemia.