Mode of hemolytic action of the antifungal polyene antibiotic filipin

Filipin at low concentrations rapidly hemolyzes bovine erythrocytes. Of the compounds tested, which were known a constituents of cell membranes, only cholesterol and phosphatidyl-choline prevented hemolysis. A specific complex was formed only with cholesterol. Filipin treatment caused a release of cholesterol from erythrocytes. Since all cell sterol is located in the cell membrane, the hemolytic action of filipin may be due to a displacement of cholesterol from the cell membrane thus weakening its stability. The internal pressure of the cell then could force the hemoglobin through the defective membrane.