Characterization of alterations in mitochondrial respiration in paclitaxel-sensitive (A549) and paclitaxel-resistant (A549/Taxol) cells. (A) A549 and A549/Taxol cells at 200× magnification. (B) Transmission electron microscopy of mitochondrial morphology. (C) Oxygen consumption. Cells were cultured in DMEM using glucose or glutamine as a carbon source. (D) Release of 14C-CO2. Cells (5 × 106) were cultured in 4 ml low-glucose DMEM containing 0.5 μCi/ml 14C-6-glucose for 2 h. Released 14C-CO2 was measured. (E) Mitochondrial membrane potential was calculated using the following formula: JC-1 intensity of Q2 quadrant / JC-1 intensity of Q4 quadrant. (F) Mitochondrial oxidative phosphorylation complex I enzyme activity. (G) Comparative analysis of the expression of key glycolysis enzymes. (H) p53expression in A549 and A549/Taxol cells by western blot analysis. *P < 0.05. Data are mean ± standard error of the mean (SEM) of three independent experiments.