Compound C acts as an inhibitor of mitochondrial complex I and inhibits hypoxia-dependent HIF-1 α stabilization. A. 143B cells were incubated at 1% O2 for 4 hours in the presence of Compound C (20 μM, 40 μM and 80 μM). Whole cell lysates were separated by 10% SDS gel and probed for HIF-1α. B-D. Mouse liver mitochondria were isolated by differential centrifugation in mitochondrial isolation buffer containing 280 mM sucrose, 10 mM Tris (pH7.4) and 1 mM EDTA as described in  and subjected to one freeze thaw cycle before measurement. Oxygen consumption of mouse liver mitochondria was measured with 2.5 mM NADH, 5 mM succinate or 0.2 mM TMPD/1 mM ascorbate as respiratory substrates and 80 μM Compound C in mitochondrial isolation buffer using a Clark-type oxygen electrode at 37°C. The results shown are representative of 2 independent experiments.