Effect of filipin on liposomes prepared with different types of steroids.

The action of the polyene antibiotic filipin on the permeability of liposomes prepared with lecithin and several plant and other steroids was studied. The effect of filipin was found to be dependent upon the type of steroid incorporated into the membrane. The interaction of filipin with steroids was found to be related both to the functional group at the 3-position and the aliphatic chain of the steroid. Complex formation of the steroid with filipin in aqueous solutions, as detected by ultraviolet spectrophotometry, correlated with the ability of filipin to increase the permeability of the liposomes.From these results it was suggested that the action of filipin could be used as a diagnostic tool to determine the presence of different steroids in plant membranes. Differences in the sensitivity of subcellular organelles to filipin may be due to differences in the steroid composition of their membranes.