FLUORESCENCE ANALYSIS OF CARRIER RAT AND HUMAN ERYTHROCYTES LOADED WITH FITC-DEXTRAN

Rat and human erythrocytes are inherently different with respect to sl ow dialysis encapsulation used in preparing carrier erythrocytes, The incorporation process, commonly measured with radioactive tracers, is always larger in human erythrocytes, mainly because the rat carrier ce lls are more fragile, When FITC-Dextran (Dx) is used in the encapsulat ion process, and loaded rat and human RBCs are studied by fluorescence intensity, some additional events are evident, Not all cells of each population appear with a fluorescence signal, and not all show similar fluorescence intensity, Human RBCs show a higher percentage of marked cells and a higher fluorescence intensity than rat RBCs, Two populati ons, of high and low fluorescence, appear in FITC-Dx loaded rat erythr ocytes, The human loaded RBCs show a similar peak distribution togethe r with another peak in the middle scale of fluorescence, Therefore, a heterogeneity in the cell population as a result of the encapsulation process is manifested for both species, The fractionation of RBCs, loa ded with either FITC-Dx or I-125-CA, by centrifugation on Ficoll-Paque reveals that the low density cells have much more substance incorpora tion than the counterpart cell subpopulation in the pellet. Therefore, the cell modifications produced by the encapsulation process are inde pendent of the substance being incorporated. On the other hand, FITC-D x, but not I-125-CA, shows a certain degree of association to RBCs mem branes, especially in humans. (C) 1996 Wiley-Liss, Inc.