Determination of the content of nonfilterable cells in erythrocyte suspensions as a function of the medium osmolality

Abstract

The results of most filtration assays for deformability of erythrocytes do not distinguish whether the entire population or only its small fraction exhibits abnormal Theological properties. We developed a simple filtration method for determination of the percentage of nonfilterable cells in erythrocyte suspension using membrane filters with mean pore diameter of 3.1 μm. This method makes it possible to detect even minor abnormal subpopulations in erythrocyte suspensions. The flow rate of buffer depends on the number of free pores of a filter. The plot of the number of pores clogged by nonfilterable cells vs the total number of erythrocytes that were allowed to pass through the filter had a linear portion, with a slope representing the relative content, Z%, of nonfilterable cells in the suspension. We determined Z% for various medium osmolalities u and used the data to derive the distribution of erythrocytes in u cr ( u cr is the maximum value of u at which an erythrocyte cannot pass through a pore of a given filter because of geometric limitations). The distribution of u cr in suspension of normal erythrocytes has a ma×imum of about 200 mOsm/kg and a half-width of about 20 mOsm/kg. The distributions of u cr are altered in normal erythrocyte suspensions at decreased pH values, in cryopreserved and ATP-depleted erythrocyte suspensions and in erythrocytes from a xerocytosis patient.