Flux control coefficients for Pi- and adenine nucleotide translocator in rat liver mitochondria after Fe2+/ascorbate...

In the early phase of iron/ascorbate induced peroxidation in rat liver mitochondria a progressively diminished active and uncoupled respiration, likely caused by an attack at the level of the respiratory chain was established, whereas the transmembrane potential (delta psi) under phosphorylating conditions did, however, not reflect this inhibition. A tentative explanation for this behaviour was suggested on the basis of an impairment of both membrane potential generating and consuming processes. By measurements of the velocity of mitochondrial 32Pi-uptake during the time course of peroxidation an inhibition of the Pi-carrier was detected. The calculated flux control coefficients for the Pi- and ATP/ADP-translocator indicate that the last one exerts a large control independent on the respiration rate during the initial phase of peroxidation. The data show that the predominant step in the control of oxidative phosphorylation at the site of the consumers must be attributed to the ATP/ADP-exchanger.