Inhibition of mitochondrial calcium ion transport by an oxo-bridged dinuclear ruthenium ammine complex

Biochemistry. 1991 May 21;30(20):4949-52. doi: 10.1021/bi00234a016.


Ruthenium red is a well-known and effective inhibitor of the mitochondrial Ca2+ uniporter; however, Reed and Bygrave [(1974) FEBS Lett. 46, 109-114] tentatively attributed this inhibition to a colorless impurity present in commercial samples of ruthenium red (RR). This component has now been isolated and a derivative, (mu-O) [(HCO2)(NH3)4Ru]2Cl3, structurally characterized. The active species in solution appears to be the symmetrical oxo-bridged ion, [X(NH3)4Ru-O-Ru(NH3)4X]3+, where X = Cl- or OH-. Its absorption spectrum shows a maximum at 360 nm. The dinuclear ruthenium ammine complex inhibits Ca(2+)-stimulated respiration of rat liver mitochondria with an I50 of 3.5 pmol/mg of protein compared to the value of 60 pmol of RR/mg of protein. The inhibition by the dinuclear compound is noncompetitive with Ca2+. Respiration-linked swelling of mitochondria induced by Cd2+ also responds similarly to both the dinuclear complex and RR. A close correlation was observed between binding to mitochondria as monitored with 103Ru-labeled dinuclear complex and inhibition of Ca2+ transport. A Scatchard plot yielded estimates of maximum specific binding and dissociation constant of 7.5 pmol/mg of protein and 1.3 nM, respectively. The inhibitor has the characteristics of a satisfactory affinity ligand for purification of the uniporter.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Calcium / pharmacology
  • Kinetics
  • Mitochondria, Liver / drug effects
  • Mitochondria, Liver / metabolism*
  • Mitochondrial Swelling / drug effects
  • Models, Molecular
  • Organometallic Compounds / chemical synthesis
  • Organometallic Compounds / chemistry
  • Organometallic Compounds / pharmacology*
  • Oxygen Consumption / drug effects
  • Rats
  • Ruthenium / chemistry
  • Ruthenium / pharmacology*
  • Spectrophotometry


  • Organometallic Compounds
  • (mu-oxo)bis(formatotetraammineruthenium)
  • Ruthenium
  • Calcium