Figure 3: Effects of girinimbine on A549 cells lysosome acidic environment. Cells were incubated with different concentrations of girinimbine for 24 h, stained with acridine orange and analyzed by ArrayScan HCS system. Control group corresponds to untreated cells. Acridine orange is a metachromatic fluorochrome and a weak base that exhibits red fluorescence when highly concentrated in acidic lysosomes. (a) Normal lysosome acidic environment (arrow). Notice the weak lysosome staining pattern and cytoplasm acidification (arrowhead) in cells treated with chloroquine (b) and girinimbine (c), indicating lysosomal membrane permeabilization. Magnification 20X. The mean fluorescent intensity produced by the acridine orange was quantitatively measured (Figure 3(d)).