Calcium efflux parallel to total phosphate retention in rat liver mitochondria

Phosphate efflux from uncoupled rat liver mitochondria was completely inhibited when mersalyl plus butylmalonate and ATP were added to a sucrose suspending medium. Despite the total retention of phosphate a calcium efflux was observed even in presence of ruthenium red. Under the above conditions no phosphate is transported in association with the ADP/ATP carrier. While mersalyl completely blocked the phosphate release induced by ruthenium red or EGTA from coupled mitochondria it only partially inhibited the CA2+-efflux. The inhibition of Ca2+ efflux was almost completely abolished in the presence of acetate. The existence of a co-transport of Ca2+ associated with phosphate is discussed.