Fig. 1. Cytofluorimetric analysis of CL distribution in HL-60 (first and second rows) and HCW-2 cells (third and fourth rows). Cells were stained with different concentrations of NAO, resulting in different red fluorescence (FL3) histograms. Here, histograms show representative examples of the doses 2.5, 8, 10, and 35 µM. The median intensity value (in linear scale) of 35 µM NAO dose was then considered as 100%, and the other values are shown as percentages of the maximum fluorescence intensity (i.e., that were obtained with the 35 µM dose). Arrows indicate the first plateau of FL3, corresponding to the percentage of CL present on the outer leaflet of the mitochondria inner membrane. Left column: control cells; right column: cells treated with 5 µM STS for 3 h. One experiment representative of four is shown.