MOLECULAR SIZE-DEPENDENT LEAKAGE OF INTRACELLULAR MOLECULES FROM FROG SKELETAL-MUSCLE FIBERS PERMEABILIZED WITH BETA-ESCIN

The permeability of beta-escin-treated cell membrane nas characterized in term of the permeant molecular size, by monitoring the leak of cytoplasmic molecules in frog skeletal muscle fibers. With a low concentration of beta-escin (5 mu M), most of the cellular ATP was lost within 30-40 min (as revealed by rigor force generation), whereas a fluorescence-labeled dextran injected into the cytoplasm (similar to 10 kDa) and cytoplasmic proteins (14-80 kDa) slowly leaked out of the cell. A high concentration of beta-escin (50-100 mu M) accelerated the leak of large molecules. Therefore, low concentrations of beta-escin may be used as a means of permeabilizing the cell membrane to relatively small molecules, while retaining a major fraction of the cellular macromolecules.