EFFECT OF CALCIUM ON THE TRANSLOCATION OF ADENINE-NUCLEOTIDES IN RAT-LIVER MITOCHONDRIA

The effect of Ca2+ on the adenine nucleotide translocase activity of intact rat liver mitochondria has been studied. The results indicate that in mitochondria which have been allowed to accumulate Ca2+, the activity of the translocase is strongly diminished; half-maximal inhibition is attained when approximately 40 nmol of Ca2+ are accumulated/mg of mitochondrial protein. Inhibition of electron transport or uncoupling prevents the Ca2+-induced inhibition of translocase activity; inhibition of Ca2+ uptake by ruthenium red also prevents the inhibition of the exchange. These experiments indicate that internal, but not external Ca2+ is responsible for the inhibition of adenine nucleotide translocase activity. Inhibition of the exchange activity by Ca2+ occurs even in conditions in which external adenine nucleotide concentrations are rate-limiting. © 1979.