Ouabain and valinomycin induced mitochondrial membrane depolarization in LN229 cells. The mitochondrial membrane potential was assessed using the fluorescent dye TMRM in LN229 cells. A. TMRM (200 nM) was added into the medium to stain the live cells for 30 min. The intensity of TMRM fluorescence images is a reflection of the mitochondrial membrane potential. The reduction and disappearance of TMRM staining was seen 6 hrs after ouabain (1 μM) and valinomycin (10 μM) treatment. B. Quantification of TMRM fluorescence intensity after 6 hrs of ouabain treatment. Both ouabain and valinomycin induced a significant loss of the mitochondrial membrane potential in LN229 cells. DMSO was a vehicle negative control. The fluorescent intensity was quantified using the NIH Image J software. * P < 0.05 vs. controls.