STUDIES ON OXIDATIVE PHOSPHORYLATION——Ⅰ.THE EFFECT OF 2,4-DINITROPHENOL ON THE OXIDATION OF SUCCINATE

<正> The effect of 2,4-dinitrophenol on the oxidation of succinate in rat-liver mitochondria has been studied with the vibrating platinum microelectrode. It has been found that DNP stimulated the rate of respiration only for a short period of about one minute, and this was followed by an inhibited phase of the oxygen-uptake. The inhibited phase no longer appeared if inorganic phosphate was added before, together with or shortly after the addition of DNP when the respiration was still in the stimulated phase, whereas after the inhibited phase had set in, the addition of inorganic phosphate had no stimulatory effect on the rate of respiration. Neither ADP nor ATP could directly restore the respiratory activity of the above system in the inhibited phase. Slow increase in respiration of the DNP-inhibited system was observed after short incubation with ATP. Results presented in the present paper do not offer support to the hypothesis that the accumulation of oxaloacetate is the direct cause of the inhibition of succinate oxidation by DNP. It has been suggested as a working hypothesis that a high energy phosphate intermediate of oxidative phosphorylation is essential for maintaining a high rate of oxidation of succinate in intact mitochondria.