OXALOACETATE-DEPENDENT CA2-LIVER MITOCHONDRIA( TRANSPORT IN RAT)

The effect of oxaloacetate on Ca2+ transport by isolated rat liver mit ochondria has been studied Under aerobic conditions mitochondria incub ated in the presence of oxaloacetate (OA) accumulated Ca2+ in a Ruthen ium Red (RR) and uncoupler sensitive manner. Oxaloacetate in the prese nce of inhibitors of the respiratory chain and ATPase also supports sl ow accumulation (5 nmoles/mg protein per min) of a limited amount of c alcium by mitochondria. Under these conditions ADP, pyruvate, succinat e, and isocitrate increase both the rate of OA-dependent calcium trans port and the amount of calcium accumulated In all cases (excepting iso citrate) OA-dependent Ca2+ accumulation is blocked by low arsenite con centrations. Addition of OA to mitochondria treated by inhibitors of t he respiratory chain and ATPase increases [NAD(+)].[NADPH]I[NADH].[NAD P(+)] and mitochondrial transmembrane potential generation. Ammonium c hloride decreases the rate of oxaloacetate-dependent calcium accumulat ion. The data presented suggest that mitochondrial OA-dependent Ca2+ a ccumulation first described here is mediated by energy-dependent mitoc hondrial transhydrogenase. The data are discussed in accordance with t he problem of OA-induced calcium release.