Effect of dextran 40 on endothelial binding and vesicle loading of ferritin in rabbit aorta

The effects of dextran 40 on endothelial binding and vesicle loading of cationized (CF, pl greater than 9.0) and anionic (AF, pl = 3.8 to 4.2) ferritins were investigated in the rabbit aorta. After two minutes of in situ perfusion, both ferritin species entered luminal vesicles and bound to the luminal endothelial membrane with a high surface density at vesicle necks. With CF, the presence of 5% dextran 40 did not change the fraction of vesicles loaded, the number of particles per vesicle, or the average density of particles bound to the luminal membrane, but did reduce the average density of particles adhering to vesicle necks. With AF, dextran 40 increased the percentage of vesicles filled, the average number of particles per loaded vesicle, the membrane particle density, the percentage of loaded vesicle necks, and the average density of particles adhering to vesicle necks. Application of gel chromatography and electrophoresis and determination of carbohydrates in the ferritin and dextran perfusates by the anthrone method after precipitation of the ferritin demonstrated that the dextran and ferritin did not conjugate. We hypothesize that the dextran binds to the endothelial membrane and increases its affinity to AF possibly by shielding negatively charged sites and that it binds in such a way as to offer little steric hindrance to AF particles entering vesicles.