The targets of 2,2',5,5'-tetrachlorobiphenyl in the respiratory chain of rat liver mitochondria revealed by modular kinetic analysis

The response of the respiratory subsystem of oxidative phosphorylation to the environmental pollutant, 2,2',5,5'-tetrachlorobiphenyl (2,2',5,5'-TCB) was investigated by modular kinetic approach. The effects of 20 M 2,2',5,5'-TCB on the activity of the respiratory chain modules in rat liver mitochondria oxidizing succinate (+ rotenone) in state 3 were assessed. The toxin inhibited the rate of respiration by 23%. Analysis around cytochrome c revealed that 2,2',5,5'-TCB inhibited both cytochrome c-oxidizing and - reducing modules. The toxin inhibited also CoQ-oxidizing module, however it did not affect the kinetics of CoQ-reducing module. Taken together, these data indicated that 2,2',5,5'-TCB inhibited cytochrome bc₁ but had no effect on succinate dehydrogenase.