Investigation of polyene macrolide antibiotic-induced permeability changes in vesicles by 31P nuclear magnetic...

The permeability of egg yolk lecithin (EYL) vesicles to Pr3+ has been measured by 31P nuclear magnetic resonance (nmr) spectroscopy. Measurable Pr3+ leakage into the internal aqueous compartment of EYL vesicles at ambient (21 degrees C) temperature required the presence of small (7--10 mol%) amounts of dicetyl phosphate (DCP). The permeability of DCP-containing vesicles is decreased by incorporation of sterol (cholesterol greater than ergosterol approximately 5.6-dihydroergosterol greater than zymosterol) into the lipid bilayer. Addition of the polyene macrolide antibiotic, nystatin, to DCP-containing EYL vesicles with and without sterol resulted in increased Pr3+ permeability at the three temperatures studied (21--37.5 degrees C). Permeability changes observed upon addition of nystatin to sterol-impregnated, DCP-containing vesicles varied with sterol structure: ergosterol approximately 5,6-dihydroergosterol greater than cholesterol approximately zymosterol. These results are compared with other polyene macrolide induced permeability changes on model and natural membrane systems. Permeability changes induced by nystatin in sterol-free EYL vesicles were generally greater than for comparable sterol-containing vesicles. This is attributed to a nonspecific interaction of the antibiotic with the latter vesicles.