Flow cytometry as a new method for the measurement of electrophoretic mobility of erythrocytes using membrane charge staining by fluoresceinated polycations.

The binding of FITC-labeled poly-L-ornithine and poly-L-lysine to fresh or neuraminidase treated human, rat or rabbit erythrocytes was investigated by simultaneous cell volume and cell membrane fluorescence measurements in a flow cytometer. The cell volume was converted into cell surface and the distribution curve of the fluorescence/micrometer2 cell surface was calculated from all histogram classes by a computer program. The mean fluorescence/micrometer2 cell surface as a measure of the density of the negative charges on the cell surface was directly proportional to the elctrophoretic mobility of the erythrocytes, showing that polycation binding can effectively be used for the measurement of the electrophoretic mobility of erythrocytes. The computer fitting of the experimental two parameter histograms by two dimensional Gaussian normal distributions was found to be a very efficient way of data reduction, and a good separation of overlapping cell clusters was possible even in the case of low total numbers of cells in the histogram.