The assumption that nitric oxide inhibits mitochondrial ATP synthesis is correct

The assumption that reversible inhibition of mitochondrial respiration by n itric oxide (NO.) represents inhibition of ATP synthesis is unproven. NO. c ould theoretically inhibit the oxygen consumption with continued ATP synthe sis, by acting as an electron acceptor from cytochrome c or as a terminal e lectron acceptor in stead of oxygen, We report here that NO. does reversibl y inhibit brain mitochondrial ATP synthesis with a time course similar to i ts inhibition of respiration. Whilst such inhibition was largely reversible , there appeared to be a small irreversible component which may theoretical ly be due to peroxynitrite formation, i.e, as a result of the reaction betw een NO. and superoxide, generated by the mitochondrial respiratory chain. ( C) 1999 Federation of European Biochemical Societies.