The generation of reactive-oxygen species associated with long-lasting pulse-induced electropermeabilisation of mammalian cells is based on a non-destructive alteration of the plasma membrane

Chinese hamster ovary (CHO) cells in suspension were subjected to pulsed el ectric fields suitable for electrically mediated gene transfer (pulse durat ion longer than 1 ms). Using the chemiluminescence probe lucigenin, we show ed that a generation of reactive-oxygen species (oxidative jump) was presen t when the cells were electropermeabilised using millisecond pulses. The ox idative jump yield was controlled by the extent of alterations allowing per meabilisation within the electrically affected cell area, but showed a satu rating dependence on the pulse duration over 1 ms. Cell electropulsation in duced reversible and irreversible alterations of the membrane assembly. The oxidative stress was only present when the membrane permeabilisation was r eversible. Irreversible electrical membrane disruption inhibited the oxidat ive jump. The oxidative jump was not a simple feedback effect of membrane e lectropermeabilisation. It strongly controlled long-term cell survival. Thi s had to be associated with the cell-damaging action of reactive-oxygen spe cies. However, for millisecond-cumulated pulse duration, an accumulation of a large number of short pulses (microsecond) was extremely lethal for cell s, while no correlation with an increased oxidative jump was found. Cell re sponses, such as the production of free radicals, were present during elect ropermeabilisation of living cells and controlled partially the long-term b ehaviour of the pulsed cell. (C) 1999 Elsevier Science B.V. All rights rese rved.