[Creation of Delta mu(H)+ equal to 250 mV on the inner mitochondrial membrane is necessary, but not a sufficient condition for ATP synthesis].

Electron transport in the NADH-ferricyanide and succinate-->O2 chains and ATP synthesis in mitochondria under different incubation conditions have been studied. Ferricyanide which substitutes oxygen as a terminal acceptor provides the generation on the membrane potential, delta microH+, but does not initiate the functioning of the proton cycle. It is suggested that mitochondria can utilize delta microH+ only during the functioning of the redox chain under aerobic conditions. Presumably, under normal conditions oxygen implements two (but not one) functions; the second function of O2 may consist in the formation of a superoxide radical anion. Under conditions of decoupling caused by the free radical scavenger propylgallate, the ATP synthesis in mitochondria may be stimulated de novo through superoxide generation. This effect is abolished by superoxide dismutase.