Effect of cholesterol incorporation on the sensitivity of liposomes to the polyene antibiotic, filipin

Abstract

1. 1. A simple spectrophotometric assay has been developed by which the effect of lytic agents on liposomes can be conveniently determined. This method is based on the change in absorbance at 340 mμ which occurs when trapped glucose is liberated in the presence of hexokinase (EC 2.7.1.1) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49). Because the spectrophotometric assay is more sensitive (requiring lower concentrations of liposomes), it possesses several advantages over alternative procedures which have been used to study the release of trapped markers.

2. 2. It has been reported that the polyene antibiotic, filipin, did not produce a greater release of marker when cholesterol was incorporated into the liposomes. This problem has been re-examined with the spectrophotometric assay. Our results indicate that the presence of sterol does increase the sensitivity of the liposomes to the antibiotic. These observations are consistent with previous lipid monolayer and bilayer experiments and the known biological properties of the polyene antibiotics