Oxygen uptake, ATPase activity, and superoxide dismutase activity in isolated rat liver mitochondria are not influenced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate

The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) influences neither the State 3 nor the State 4 respiration in rat liver mitochondria. The respiratory control and ADP/O ratio were also unaffected by TPA. The oligomycin-sensitive ATPase activity in submitochondrial particles remained unaltered upon TPA addition, whereas the NADH oxidase activity was slightly inhibited at a very high concentration of TPA (15% decrease at 17 μM TPA). The activity of the superoxide dismutase located to the mitochondria was insensitive to the tumor promoter, and no change in the rate of H2O2 production was found on TPA treatment in vitro. Thus, the mitochondrion is not a likely candidate for the site of action of the tumor promoter.