CELL PARTITIONING IN 2-POLYMER AQUEOUS-PHASE SYSTEMS AND CELL ELECTROPHORESIS IN AQUEOUS POLYMER-SOLUTIONS - HUMAN AND RAT YOUNG AND OLD RED-BLOOD-CELLS

It has recently been found that electrophoresis in solutions of approp riately selected polymers in phosphate-buffered saline (PBS) can diffe rentiate between some closely related cell populations which have iden tical electrophoretic mobilities (EPM) in PBS (e.g., human young and o ld red blood cells (RBC); RBC from Alzheimer patients and normal indiv iduals). The EPM differences detected in polymer solutions are most li kely a consequence of cell- and polymer-specific interactions. Aspects of the relation between the electrophoresis in aqueous polymer soluti ons of native and in vitro treated young and old RBC (from human and r at) and their partitioning in a charge-sensitive dextran-poly(ethylene glycol) (PEG) aqueous phase system (i.e., a system with a Donnan pote ntial between the phases, top phase positive) have been examined furth er and are discussed. Unlike the behavior of RBC from Alzheimer patien ts and normal individuals in which an EPM difference can be detected i n PEG solutions but not in dextran, differences in EPM between human y oung and old RBC are detectable in solutions of either polymer. Select ed enzyme treatments of human young and old RBC or their fixation with aldehyde eliminates the EPM differences in dextran; while neuraminida se treatment or formaldehyde fixation of rat young and old RBC retains EPM differences in dextran between these cells. In these latter cases partitioning differences are also in evidence and are in the same dir ection as the cells' relative EPM (i.e., old RBC < young RBC). The ear lier hypothesis that cell partitioning is 'more sensitive' than cell e lectrophoresis in detecting differences in surface charge between cell s bears reexamination because human young and old RBC, which cannot be differentiated by single-tube partitioning in a charge-sensitive phas e system, have different EPM in polymer solutions. The difference betw een these cells can be detected by partitioning but only by use of a m ultiple-extraction procedure. It is then found to be in a direction si milar to the cells' relative EPM in dextran (i.e., human old RBC > you ng RBC). Rat young and old RBC have different partitions Oat old RBC < young RBC) and different EPM (also rat old RBC < young RBC). Thus, wh ile cell partitioning in a charge-sensitive dextran-PEG aqueous phase system and cell electrophoresis in polymer solution seem to reflect, a t least with these cell subpopulations, qualitatively analogous differ ences in surface properties (in that increasing partitions and EPM are concomitant), there are instances in which either of these physical m easurements discerns surface differences which escape detection by the other.