A MODIFICATION OF THE FILTRATION METHOD F OR STUDYING THE CONTENT OF NONFILTERABLE CELLS IN ERYTHROCYTE SUSPENSION

The results of filtration assays provide estimates of the deformabilit y of erythrocytes averaged over the entire suspension. These assays do not distinguish whether the entire population or only its small Fract ion exhibits abnormal rheological properties. We developed a simple me thod using a filtrometer to determine the percentage of nonfilterable (under given conditions) cells in the erythrocyte suspension. Membrane filters made of a polyethyleneterphtalate film had the mean pore diam eter of 3,1 mu m and the length of cylindrical micropores of 7 mu m. T he buffer flow rate t(b) depends on the number of free pores is a filt er. The plot of the number of pores clogged by nonfilterable cells ver sus the total number of erythrocytes passed through the filter had a l inear portion, whose slope represents the relative content Z of nonfil terable cells in the suspension. We determined Z for various medium os molalities u. These data were used to derive the distribution of eryth rocytes in u(cr), the value of u at which an erythrocyte cannot pass t hrough a pore of a given filter because of geometric limitations. The distribution maximum corresponded to 190-200 mosm for erythrocytes fro m the normal blood. This means that normal erythrocytes have the media n values of their surface area and area-to-volume ratio of 155-151 mu m(2) and 1,72-1,68 mu m(-1), respectively. The half-width of the distr ibution was approximately 30 mosm. This finding suggests that the norm al blood contains a certain fraction of erythrocytes with a decreased area-to-volume ratio. Our results showed that the distribution is alte red in various forms of anemia and in ATP-depleted erythrocyte suspens ions.