Interaction of phospholipid vesicles with rat hepatocytes

The interaction of positively and negatively charged unilamellar and multilamellar phospholipid vesicles (liposomes) with rat-liver parenchymal cells in primary monolayer culture have been studied. Radioactive liposomal phosphatidylcholine was taken up more rapidly and to a larger extent from unilamellar than from multilamellar vesicles. No significant difference in uptake characteristics was observed between vesicles of different charge. The presence of serum greatly reduced uptake of liposomal phosphatidylcholine of both unilamellar and multilamellar vesicles. This serum effect was independent of surface charge of the vesicles. When cells were preincubated with vesicles containing horseradish peroxidase and then, after removal of the vesicles, further incubated, peroxidase activity could be demonstrated in the culture medium, part of it only after addition of Triton X-100. Vesicle-entrapped [125I] albumin was taken up by the cells and rapidly hydrolyzed as indicated by the appearance of radioactivity soluble in trichloroacetic acid within minutes after starting the incubation. (Auth.)