Chlordimeform: Uncoupling activity against rat liver mitochondria

The pesticide chlordimeform N′-(4-chloro-o-tolyl)-N,N-dimethylformamidine] at 0.04 μmoles/mg protein uncouples 50% of respiratory-chain phosphorylation of rat liver mitochondria. This uncoupling activity depends on mitochondrial protein concentration and can be reversed either by the addition of bovine serum albumin or by washing. The normal inhibition of state 3 respiration by oligomycin and atractylate is completely reversed by chlordimeform. Uncoupling concentrations of chlordimeform elicit high adenosine triphosphatase activity. This activity is blocked by the above inhibitors of mitochondrial energy-transfer reactions. Evidence is presented which shows that unprotonated chlordimeform is the form effective in uncoupling. It is concluded that chlordimeform is an uncoupling agent with a potency and site of action close to but probably not identical to that of the classical uncoupler 2,4-dinitrophenol.