Figure 4

Ouabain and valinomycin induced intracellular K ⁺ depletion in LN229 cells. The K⁺ fluorescent dye PBFI-AM was used to measure the intracellular K⁺ changes of LN229 cells during ouabain and valinomycin exposures. A. PBFI images illustrated reduction in intracellular K⁺ content 24 hrs after ouabain (1 μM) or valinomycin (10 μM) treatment. B. Quantified data of PBFI imaging at 6, 12 and 24 hrs exposures to ouabain and valinomycin. By 24 hrs after exposure, ouabain and valinomycin each caused aproximatley 50% of cellular K⁺ loss. This could be equivalent to a loss of about 70 mM K⁺ from the intracellular space. DMSO was tested as the vehicle control. N = 180 cells from 3 independent assays in each group. * P < 0.05 vs. control groups. C. Cell death induced by ouabain was sensitive to a protective effect of high K⁺ extracellular medium. Around 50% of cell death was prevented in the high K⁺ medium. Cell death was measured using the MTT assay 24 hrs after exposure. The control medium contained 5 mM KCl. ^# P < 0.05 vs. ouabain group. D. Valinomycin (10 μM) induced cell shrinkage after 3, 6, 12, 24 hrs exposure in LN229 cells. * P < 0.05 vs. control group.