CORRELATION BETWEEN ELECTRIC-FIELD PULSE INDUCED LONG-LIVED PERMEABILIZATION AND FUSOGENICITY IN CELL-MEMBRANES

Electric field pulses have been reported to induce long-lived permeabi lization and fusogenicity on cell membranes. The two membrane property alterations are under the control of the field strength, the pulse du ration, and the number of pulses. Experiments on mammalian cells pulse d by square wave form pulses and then brought into contact randomly th rough centrifugation revealed an even stronger analogy between the two processes. Permeabilization was known to affect well-defined regions of the cell surface. Fusion can be obtained only when permeabilized su rfaces on the two partners were brought into contact. Permeabilization was under the control of the pulse duration and of the number of puls es. A similar relationship was observed as far as fusion is concerned. But a critical level of local permeabilization must be present for fu sion to take place when contacts are created. The same conclusions are obtained from previous experiments on ghosts subjected to exponential ly decaying field pulses and then brought into contact by dielectropho resis. These observations are in agreement with a model of membrane fu sion in which the merging of local random defects occurs when the two membranes are brought into contact. The local defects are considered p art of the structural membrane reorganization induced by the external field. Their density is dependent on the pulse duration and number of pulses. They support the long-lived permeabilization. Their number mus t be very large to support the occurrence of membrane fusion.