Behaviour of isolated rat and human red blood cells upon hypotonic-dialysis encapsulation of carbonic anhydrase and dextran.

Rat and human carrier red blood cells (RBCs) were prepared by hypotonic-dialysis encapsulation. The standard conditions used for encapsulation were 80 mOsm/kg for 60 min. The encapsulation behaviour of rat and human RBCs was studied using radiolabelled carbonic anhydrase and fluorescently labelled dextran. Both markers are incorporated to slightly greater extents by human than by rat RBCs by hypotonic treatment. Cell recovery of rat and human RBCs loaded with either carbonic anhydrase or fluorescent dextran accounted for 49% and 80% respectively. The cellular integrity of the loaded cells was revealed by the presence of fluorescence labelling in rat and human RBCs. Fluorescence studies showed an increase of size dispersion in loaded rat and human RBCs, giving cellular volume variations in both types of cells resulting from the encapsulation procedure. Two loaded cell populations were evident in both species, one with high fluorescence content and another with background staining. Apparently the proportion of high fluorescently labelled loaded cells was higher in the case of the human RBCs. A reduced level of fluorescence labelling was observed in rat and human RBC membranes, which indicates a process of adsorption of dextran to the membranes.