Hemolysis during filtration through micropores: a scanning electron microscopic and hemorheologic correlation.

Abstract The resistance of normal human erythrocytes to mechanical hemolysis was studied by filtration (pressure gradient up to 74 cm Hg) through polycarbonate sieves with mean pore diameters of 2.2–4.4 μ. Hemolytic release of hemoglobin and potassium increased with an elevation of filtration pressure and a reduction in pore size. In 2.2-μ sieves, half-maximum release of intracellular content occurs at a filtration pressure of approximately 12 cm Hg. Under a given sieving condition, the release of hemoglobin was approximately one-half that of potassium, suggesting membrane holes of approximately 100 A in diameter. Hemolytic release of intracellular content was accompanied by reduction in resistance of the erythrocyte suspension during filtration. The changes in erythrocytes during and after filtration have been studied with scanning and transmission electron microscopes. With an elevation of pressure or with a reduction in pore size, increasing numbers of RBC become microspherocytes and spur cells with membrane protrusions. These changes in RBC shape due to mechanical stress during passage through small pores are the same as those observed in human hemolytic anemia of the microangiopathic type.