The Role of Inorganic Phosphate in the Release of Ca2+ from Rat‐Liver Mitochondria

Abstract

The effect of inorganic phosphate on Ca2+ retention was investigated using phosphate-depleted liver mitochondria. Phosphate induces the release of Ca2+ through an efflux route insensitive to ruthenium red. This effect is not due to functional or structural damage, since mitochondria maintain their membrane potential during phosphate-induced Ca2+ efflux. Direct enzymatic measurement of mitochondrial pyridine nucleotides has established that changes in their redox state (i.e., increased oxidation) do not play a role in the phosphate-effect. The phosphate-induced Ca2+ and phosphate do not coincide; the release of phosphate precedes that Ca2+.