The uptake of distearoylphosphatidylcholine/cholesterol liposomes by rat intestinal sacs in vitro.

The uptake of free and liposome-entrapped 125I-labelled polyvinylpyrrolidone was measured in an intestinal sac preparation from adult rats. At an equal concentration of 125I-labelled polyvinylpyrrolidone, the rate of uptake of the liposome-entrapped macromolecule by the tissue was over 4-times that of the free macromolecule. The quantity of 125I-labelled polyvinylpyrrolidone present in the serosal fluid of gut sacs, cultured for 2 h, was 1.8-times greater when the macromolecule was entrapped in liposomes than when it was free in the culture medium. When gut sacs were cultured with liposome-entrapped macromolecule, approx. 50% of the total 125I-labelled polyvinylpyrrolidone present in the serosal fluid was associated with a 100 000 X g liposomal pellet.