Ruthenium red as a carrier of electrons between external NADH and cytochrome C in rat liver mitochondria

Exogenous NADH is oxidized by rat liver mitochondria when ruthenium red (2μM) is present in the medium. The oxidation is insensitive to rotenone and antimycin A, but sensitive to KCN, and is markedly reduced in a saline medium or in the presence of divalent cations. The same effect of ruthenium red can be seen in mitochondria depleted of the outer membrane. This suggests that ruthenium red acts as a mediator of electrons between NADH and cytochrome c. This is also supported by the observation that ruthenium red can replace N,N,N 1,N 1-tetramethyl-p-phenylenediamine (TMPD) in the oxidation of ascorbate by mitochondria. The effect of ruthenium red is abolished by LaCl 3.