The use of macromolecular protease inhibitors to study liposome-cell interactions

A method is introduced that quantitates the release of a high molecular weight compound from small unilamellar vesicles. The technique is based on the liposomal encapsulation of trypsin inhibitor from bovine lung. Because liposomes are impermeable to all components of the test system (inhibitor, enzyme, macromolecular substrate), only the free inhibitor released from disturbed liposomes is measured. Using this technique, the exit of the macromolecular solute from liposomes induced by erythrocyte ghosts was studied. The results were compared with the leakage of a low molecular weight fluorescent marker. They indicate that, especially during the first hours of incubation, ghost-induced release of solutes is dependent on their size.