Introduction

Exposure of cells to strong electric fields can cause both reversible and irreversible cell membrane behaviour through the occurrence of transient pores. Such pores now are believed to occur whenever the transmembrane potential, U(t), reaches values somewhat above normal resting potentials, and have been observed over the range 200 mV < U(t) < 1500 mV. Although the terminology relating to strong field effects has changed as understanding has developed, here the term ‘electroporation’ is used to refer to the occurrence of significant membrane pores due to electric fields. Once formed, the transient pores can have a variety of consequences, including both reversible and irreversible membrane phenomena. The irreversible event of rupture may occur by two quite different processes. A prompt rupture process occurs in planar bilayer membranes. A hypothesis for cell membrane rupture is that a portion of a cell membrane can experience this type of rupture if the boundaries of that portion interact with cell structures such as a cytoskeleton. In an artificial planar bilayer membrane, the prompt rupture of the cell membrane arises from the immediate interaction of an elevated transmembrane potential with transient aqueous pores. The rapidly changing pore population leads to the formation of one or a small number of supracritical pores, i.e. pores with radii greater than a critical radius, rc, which then expand until the membrane is destroyed.