Interaction of polysaccharides with plasma membranes—I. Interaction of human erythrocytes with degraded iota carrageenans and the effect of dextran and DEAE dextran

Abstract

The effect of dextran, diethylaminoethyl (DEAE) dextran, iota carrageenan, (CG) and combinations of these polymers on the aggregation of human erythrocytes has been studied. Higher molecular weight fractions of CG are much more effective than low molecular weight fractions in enhancing erythrocyte aggregation as observed by sedimentation and photo microscopy. The low molecular weight fraction M_n 9,700 of CG is not competitive with the high molecular weight fraction in effecting sedimentation. Dextran of M_w 170,000 does not appreciably increase the sedimentation of erythrocytes compared to controls up to a concentration of 5 mg/ml. However, dextran enhances the sedimentation of erythrocytes brought about by 145,000 molecular weight CG. Size distribution curves and photomicroscopy for erythrocytes incubated with CG indicate that the enhanced sedimentation of erythrocytes by CG is not due to a change in density of the erythrocytes. Low concentrations of DEAE dextran (⩾ 0.46 mg/ml) greatly enhance the sedimentation of erythrocytes by CG while higher concentrations of DEAE dextran (⩽ 2.3 mg/ml) cause erythrocytes to sediment at the same rate as controls. Sedimentation of erythrocytes incubated with 1.8 mg/ml CG, M_n 145,000, as a function of DEAE dextran concentration shows an initial increase in sedimentation rate of erythrocytes at 0.46 mg/ml DEAE dextran and then a decrease to control levels at 2.3 mg/ml. These results are interpreted in terms of the ability of the polymers to interact simultaneously with each other and with the erythrocyte surface.