Effects of amphotericin B and its methyl ester on plasma membranes of Candida albicans and erythrocytes as examined by freeze-fracture electron microscopy.

Freeze-fracture electron microscopy of the plasma membranes of Candida albicans yeast cells and red blood cells treated with amphotericin methyl ester and amphotericin B showed that amphotericin B (50 micrograms ml-1) caused extreme aggregation of intramembranous particles on the protoplasmic fracture face of the C. albicans membrane, and a marked reduction of the density of intramembranous particles. On the other hand, the rearrangement of intramembranous particles induced by amphotericin methyl ester (50 micrograms ml-1) produced elevations of the particle-free membrane domains toward the outside of the cells, so that the particles were aggregated in linear furrows surrounding these elevations on the protoplasmic fracture face, and the corresponding ridges on the exoplasmic fracture face. The density of intramembranous particles was greatly reduced on the protoplasmic fracture face. Both polyenes produced only small changes in the erythrocyte membranes at the same concentration. These results suggest that amphotericin methyl ester affects the ergosterol-containing membranes more than amphotericin B, and that ergosterol has a higher sensitivity for these two polyene antibiotics than cholesterol.