FIG. 5.

Mild mitochondrial uncoupling has no adverse effect on mitochondrial ATP production. A: Hepatocytes expressing DLP1-K38A for 24 h had a higher OCR than control cells upon oligomycin treatment, indicating an increased proton leak. B: The calculated leak ratio showed a statistically significant increase of the proton leak upon 24-h DLP1-K38A expression compared with the control (n = 8; *P < 0.05). C: Oligomycin-sensitive ATP levels (60-min oligomycin treatment) indicated little effect of 24-h DLP1-K38A expression on mitochondrial ATP-producing capacity, whereas 48-h DLP1-K38A expression significantly decreased the ATP production from mitochondria (n = 9; *P < 0.01). Error bars are SEM. D: Oxygen consumption was measured in the presence of oligomycin with increasing concentrations of FCCP. OCR measurements indicated that FCCP concentrations at 100–200 nmol/L induce a mild uncoupling, resulting in small increases of the OCR. FCCP concentrations higher than 1 μmol/L cause maximum uncoupling and thus the maximum OCR. n = 6. E: Cellular ATP contents were measured in the presence and absence of 30-min treatment of oligomycin (Olm). Oligomycin-sensitive ATP content (ATP produced from mitochondria) did not decrease in 100 nmol/L FCCP that induced a mild uncoupling. Higher concentrations of FCCP (1–2 μmol/L) decreased mitochondrial ATP production, which was compensated by increases of glycolytic ATP generation. Total cellular ATP contents diminished drastically with 5–10 μmol/L FCCP (n = 6). Error bars are SEM.