Characteristics of the active transport of Ca2+ by submitochondrial vesicles

Inner membrane vesicles have been prepared by cholate treatment of rat liver mitoplasts. The vesicles can actively accumulate Ca2+ in the absence or presence of inorganic phosphate. The uptake is inhibited by ruthenium red and uncouplers of oxidative phosphorylation. Like in intact mitochondria the driving force for the uptake reaction seems to be the negative inside membrane potential generated during the oxidation of substrates. The level of antimycin-A-sensitive reduction of ferricyanide by succinate indicates that the cholate inner membrane vesicles are about 70% right side out. Using cytochrome-c-extracted inner membrane vesicles it can be shown that only those which have the same right-side-out polarity as intact mitochondria can actively accumulate Ca2+.