EFFECT OF AMPHOTERICIN-B ON CHOLESTEROL-CONTAINING LIPOSOMES OF EGG PHOSPHATIDYLCHOLINE AND DIDOCOSENOYL PHOSPHATIDYLCHOLINE - REFINEMENT OF MODEL FOR FORMATION OF PORES BY AMPHOTERICIN-B IN MEMBRANES

1. (1) Binding and K+-permeability measurements were performed on egg and 22 : 1c 22 : 1c-phosphatidylcholine liposomes with or without cholesterol. 2. (2) Amphotericin B binds specifically to cholesterol in both types of liposome despite the difference in bilayer thickness. 3. (3) Addition of amphotericin B to one side of the cholesterol-containing egg phosphatidylcholine bilayers induces a fast K+ efflux from the outermost compartment of the liposomes. In contrast, the total K+ content of sonicated unilamellar cholesterol-containing egg phosphatidylcholine vesicles is released by amphotericin B. 4. (4) Amphotericin B addition to one side of the cholesterol-containing 22 : 1c 22 : 1c-phosphatidylcholine liposomes does not cause a change in K+ permeability. The presence of amphotericin B on both sides of the bilayer, however, induces an increase in K+ permeability. 5. (5) A model is proposed which accounts for the effect of bilayer thickness on the amphotericin B-induced permeability changes in membranes. © 1978.