A permeability change in Ehrlich ascites tumor cells caused by dextran sulfate and its repair by ascites fluid or Ca2+ ions

Exposure of Ehrlich ascites tumor cells to the polyanion dextran sulfate impaired the active transport of α-aminoisobutyric acid and made the cells nonspecifically permeable to sorbitol and erythrosin B. Subsequent incubation with ascites fluid from tumor-bearing mice restored active transport and repaired the permeability barrier in dextran sulfate-treated cells. Ascites fluid was ineffective after dialysis or the addition of ethylene glycol bis(β-aminoethyl ether)-N,N′-tetraacetic acid, suggesting the involvement of Ca²⁺ ions in repair. Treatment with CaCl₂ and glucose under specific conditions restored the transport activity of dextran sulfate-treated cells about three-fourths as effectively as was the case for ascites fluid. This procedure, which involves chemically characterized materials, may be advantageous when one wishes to incorporate impermeable substances into the cells.