Red blood cell permeabilization by hypotonic treatments, saponin, and anticancer avicins

Plasma membrane permeabilization by saponin and anticancer avicins was studied using light dispersion measurements, since high correlation between light dispersion changes and hemolysis has been demonstrated. Nevertheless, we observed that rat red blood cell swelling in moderately hypotonic media was accompanied by up to 20% decrease of light dispersion, when hemolysis was not yet detectable. Avicin G and avicin D were significantly more efficient than saponin in inducing cytotoxicity in PC3 human prostate cancer cells. We found that the preincubation of avicins with the plasma membrane, but not with the cytosolic fraction of previously lysed red blood cells, completely protected fresh cells against permeabilization. The data suggest that the plasma membrane can tightly bind the avicins, but not the saponin. Using the "osmotic protection" method with 100. mOsm PEGs of increasing molecular weight in isotonic media, the size of the pores generated by avicin G and avicin D in the plasma membrane was estimated to be higher than the hydrodynamic radius of PEG-8000. The obtained results indicate that the anticancer activity of avicin G and avicin D could be related, at least partially, to their high ability to permeabilize biological membranes. These data might represent interest for possible applications of these anticancer drugs in vivo.