Uptake by rat peritoneal macrophages of 125I-labelled polyvinylpyrrolidone entrapped within liposomes.

Abstract

Rat peritoneal macrophages in vitro capture 125I-labelled polyvinylpyrrolidone entrapped within either negatively or positively charged liposomes more rapidly than they do the free macromolecule. The uptake of negatively charged liposomes was linear with time over 10 h, whilst the uptake of positively charged ones, although more rapid, was more transient. Neither type of liposome was taken up in the presence of 2,4-dinitrophenol (100 microgram/ml), and 5 mM calcium chloride increased the uptake of negatively charged liposomes. The enhanced uptake of 125I-labelled polyvinylpyrrolidone when presented in liposomes must have been a consequence of entrapment rather than of a simple interaction between lipid and polyvinylpyrrolidone since the presence of the lipids employed or of empty liposomes had no effect on the uptake of unentrapped 125I-labelled polyvinylpyrrolidone.