ELECTROPERMEABILIZATION OF MAMMALIAN-CELLS TO MACROMOLECULES - CONTROL BY PULSE DURATION

Membrane electropermeabilization to small molecules depends on several physical parameters (pulse intensity, number, and duration). In agree ment with a previous study quantifying this phenomenon in terms of flo w (Rols and Teissie, Biophys. J. 58.1089-1098, 1990), we report here t hat electric field intensity is the deciding parameter inducing membra ne permeabilization and controls the extent of the cell surface where the transfer can take place. An increase in the number of pulses enhan ces the rate of permeabilization. The pulse duration parameter is show n to be crucial for the penetration of macromolecules into Chinese ham ster ovary cells under conditions where cell viability is preserved. C umulative effects are observed when repeated pulses are applied. At a constant number of pulses/pulse duration product, transfer of molecule s is strongly affected by the time between pulses. The resealing proce ss appears to be first-order with a decay time linearly related to the pulse duration. Transfer of macromolecules to the cytoplasm can take place only if they are present during the pulse. No direct transfer is observed with a postpulse addition. The mechanism of transfer of macr omolecules into cells by electric field treatment is much more complex than the simple diffusion of small molecules through the electroperme abilized plasma membrane.