Platelet surface charge heterogeneity: characterization of human platelet subpopulations separated by high voltage...

Washed formol-fixed normal human platelets have been separated into surface charge-dependent subpopulations using high voltage continuous flow electrophoresis. The procedure is highly reproducible and the heterogeneity profile extends over 20-25 fraction tubes on the anodal side of the entry port to the separation chamber. Fractions have been subdivided into subpopulation pools A, B and C which have mean mobilities by analytical cytopherometry extending over the range 0.81-0.91 micron/s/V/cm from the least (C) to the most (A) electronegative cells. Coulter volume differences across the profile from 5.0 to 12.8 fl correlated well with electrophoretic mobilities whereas buoyant density appeared to be an independent parameter. Analysis of surface neuraminidase-labile sialic acid of the platelets in pools A and C correlated well with differences in electrophoretic mobility, whereas a similar relationship for the alkaline phosphatase-labile phosphate moieties (also believed to be contributory to cell surface electrokinetic properties) could not be established even though in both cases the profiles of the enzyme-treated platelets showed significant shifts towards the cathode when compared with untreated cells. Titration of surface DTNB-reactive sulphydryl (-SH) groups revealed an inverse relationship between electronegativity and membrane -SH group status. This electrophoretic expression of subpopulation heterogeneity within the circulating platelet pool may have advantages in studying clinical conditions where the profiles may reflect cell surface interactions 'in vivo'.