HETEROGENEITY OF HYPOTONICALLY LOADED RAT ERYTHROCYTE POPULATIONS AS DETECTED BY COUNTERCURRENT DISTRIBUTION IN AQUEOUS POLYMER 2-PHASE SYSTEMS

Carrier rat erythrocytes loaded with exogenous substances ([I-125]carb onic anhydrase) by hypotonic-isotonic dialysis become heterogeneous ce ll populations that can be fractionated using the counter-current dist ribution (CCD) technique. Two well-defined low- and high-partition rat io, G, subpopulations are obtained in charge-sensitive dextran-polyeth ylene glycol two-phase systems. The low-G subpopulation, which contain s the most fragile and surface-altered cells, as deduced from their os motic fragility curves and partition behaviour, respectively, presents a high amount of exogenous substance incorporated (134.6 cpm/10(6) ce lls). The high-G subpopulation, that contains cells similar to the con trol or isotonically dialyzed cells presents a lower amount of exogeno us substance incorporated (69.8 cpm/10(6) cells). Cells in this high-G subpopulation seem to be fractionated, like the controls, according t o ageing as suggested by the decline of the pyruvate kinase specific a ctivity from the left- to the right-hand side of the CCD profile.