DIFFERENTIAL ELECTROPHORETIC BEHAVIOR IN AQUEOUS POLYMER-SOLUTIONS OFRED-BLOOD-CELLS FROM ALZHEIMER PATIENTS AND FROM NORMAL INDIVIDUALS

The recently reported phenomenon that red blood cells (RBC) from Alzhe imer disease (AD) patients and normal individuals, which have identica l electrophoretic mobilities (EPM) in phosphate-buffered saline (PBS), have different EPM in appropriately selected polymer solutions, has b een further explored. Of a number of in vitro treatments to which PLD and normal RBC were subjected prior to EPM measurements in bottom phas e (from a dextran-poly(ethylene glycol) (PEG) aqueous phase system) on ly trypsin eliminated the difference. Thus, the differential polymer i nteraction between AD and normal RBC, thought to be the basis for thei r dissimilar EPM, can be abolished by appropriate proteolytic modifica tion of the cell surfaces and suggests protein as a source of differen ce. Because young and old RBC from normal individuals, which have the same EPM in PBS, have different EPM in certain polymer solutions, and the RBC from AD patients have been reported to age abnormally, we also compared the young and old RBC subpopulations from these two sources. By the criterion of cell electrophoresis in polymer solutions the dif ferences between AD and normal RBC and between young and old RBC are d istinct. The EPM of AD and normal RBC differ in bottom phase or PEG bu t not in dextran solution; while the EPM of young and old RBC differ p redominantly in dextran. We speculate that since the observed differen ce in EPM of RBC from AD patients and normals depends on protein(s) ye t is anticoagulant-related (being obtained only when blood is collecte d in citrate or oxalate) it might be the result of an interaction (Ca2 +-mediated?) between the surfaces of these cells and protein component (s) of their respective, compositionally differing sera.