Electroporation of cell membrane visualized under a pulsed-laser fluorescence microscope.

Controlled permeability can be conferred to cell membranes by exposing cells to a microsecond electric pulse of sufficient intensity (electroporation). By constructing a fluorescence microimaging system with a submicrosecond time resolution we have been able to resolve temporally and spatially the events in a single cell under a microsecond electric pulse. An enormous membrane conductance, corresponding to a loss of 0.01-0.1% of the membrane area, was observed in those membrane regions where the transmembrane potential induced by the electric pulse exceeded a critical value. The conductance decreased to a low level in a submillisecond after the pulse, leaving a moderately electroporated cell.