Fig. 1.

Effect of BafA1 on the intoxication of Vero cells with CDT. (A) Vero cells were preincubated with 100 nM BafA1 or left untreated (control [con]). After 30 min, CDT (40 ng/ml CDTa plus 80 ng/ml CDTb) was added and pictures were taken after 6 h. A quantitative analysis of rounded Vero cells at the indicated time points of toxin treatment is shown. Values are means ± SD (n = 3). The significance of differences from CDT-treated cells was tested by using the Student t test (***, P < 0.0001). (B) An acidic pH triggers the membrane translocation of CDTa. Vero cells were preincubated with 100 nM BafA1 for 30 min at 37°C and then at 4°C with CDT (100 ng/ml CDTa plus 200 ng/ml CDTb; control, without toxin). Subsequently, the medium was adjusted to pH 4.5 with HCl and the cells were incubated at 37°C in this acidic medium (control, in neutral medium). Pictures were taken after 1.5 h. The percentages of round cells were determined from these pictures. Values are means ± SD (n = 3).