Fig. 3.

Enhancement of propidium (Pr) uptake by CHO cells by electrosensitization. The cells were exposed to eight, 100-μs pulses (100 Hz) at either 1.5 kV/cm (left panel) or 1.8 kV/cm (right). The treatment was performed either as a single dose or as a split dose (two trains of four pulses each with a 5-min. interval). Pr fluorescence (mean ± SE, n = 3) was normalized to the value in a sample dialyzed with digitonin. The inset shows the timeline of procedures in each of the plotted groups (‘8p’ and ‘4p’ show the approximate time of exposure to eight electric pulses (EP) and four EP, respectively; horizontal lines denote the period of incubation with propidium iodide and the time interval when fluorescence was measured). The split dose protocol caused significantly higher Pr uptake than a single dose for all time-points except 0 min. at 1.8 kV/cm (P < 0.05–0.0001, 2-tailed paired t-test). See text for more detail.