A SINGLE PARTITIONING STEP IN AQUEOUS POLYMER 2-PHASE SYSTEMS REDUCESHYPOTONIZED RAT ERYTHROCYTE HETEROGENEITY

Rat carrier erythrocytes prepared by hypotonic dialysis (80 mOsm/kg) a re a heterogeneous cell population that can be fractionated into two w ell-defined cell subpopulations by a single partition step, in charge- sensitive dextran-poly(ethylene glycol) aqueous two-phase systems. One subpopulation (65% of total cells) has a decreased cell surface charg e and is partitioned at the interface in a single step and then fracti onated by counter-current distribution as a low-G subpopulation. The o ther subpopulation (35% of total cells) has charge surface properties more like those of the untreated control rat erythrocytes. These last cells are partitioned in the top phase in a single step and then fract ionated by counter-current distribution as a high-G subpopulation. Par titioning is more effective in reducing cell heterogeneity in hypotoni zed rat erythrocyte populations than is density separation in Ficoll-p aque which only separates a small less dense cell subpopulation (5% of total cells), with the most fragile cells, from a larger and more den se cell subpopulation (95% of total cells), with a mixture of fragile and normal cells. This simple cell separation procedure quickly reduce s carrier erythrocyte heterogeneity in a single partitioning step so i t can be used to prepare cells for in vivo studies.