DETERMINATION OF THE CONTENT OF NONFILTERABLE CELLS IN ERYTHROCYTE SUSPENSIONS AS A FUNCTION OF THE MEDIUM OSMOLALITY

The results of most filtration assays for deformability of erythrocyte s do not distinguish whether the entire population or only its small f raction exhibits abnormal rheological properties. We developed a simpl e filtration method for determination of the percentage of nonfilterab le cells in erythrocyte suspension using membrane filters with mean po re diameter of 3.1 mu m. This method makes it possible to detect even minor abnormal subpopulations in erythrocyte suspensions. The flow rat e 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 num ber of erythrocytes that were allowed to pass through the filter had a linear portion, with a slope representing the relative content, Z%, o f nonfilterable cells in the suspension. We determined Z% for various medium osmolalities rt and used the data to derive the distribution of erythrocytes in u(cr) (u(cr) is the maximum value of u at which an er ythrocyte cannot pass through a pore of a given filter because of geom etric limitations). The distribution of u(cr) in suspension of normal erythrocytes has a maximum of about 200 mOsm/kg and a half-width of ab out 20 mOsm/kg. The distributions of u(cr) are altered in normal eryth rocyte suspensions at decreased pH values, in cryopreserved and ATP-de pleted erythrocyte suspensions and in erythrocytes from a xerocytosis patient.