Reversible large-scale deformations in the membranes of electrically-treated cells: electroinduced bleb formation.

Morphological changes in electrically-treated cells have been investigated by light and scanning electron microscopy. The application of 100-microseconds rectangular pulses of 1.3 kV/cm electric field to different types of cells (FBT, MEF, RAT-1, L-cells) in the physiological medium leads to the formation and growth of spherical and hemispherical protuberances of the cell membrane. The formation of such electroinduced blebs is not associated with the cells' death and is reversible. The electroinduced blebs are mainly formed at those sites of the cell membrane which are subjected to the highest voltage during the electric pulses. Increasing the tonicity of the medium by introducing 20 mM of inulin prevents the bleb formation, indicating the osmotically-dependent nature of the processes involved. When electric pulses are applied to the cells pre-treated with cytochalasin B, the formation of electroinduced blebs occurs independently from cytochalasin-induced ones originally present on such cells. Speculations are presented concerning the nature of the membrane structural changes underlying the electroinduced blebbing and their possible role in some electrically-induced processes.