Stimulation of mitochondrial Ca2+ efflux by NADP+ with maintenance of respiratory control

Experiments in this paper demonstrate that mitochondrial damage associated to NAD(P)+-induced Ca2+ efflux, is the consequence of inappropriate reaction conditions. The major findings are (i) Added oxaloacetate and acetoacetate readily oxidize NAD(P)H in intact rat liver mitochondria without causing swelling or membrane damage. (ii) Ca2+ efflux can be induced by the oxidized state of mitochondrial NADP in the presence of ATP, ADP, Pi and Mg2+, without mitochondrial swelling. (iii) Ca2+ efflux induced by NADP+ in the presence of ruthenium red causes no significant impairment of respiratory control, a sensitive measure of membrane potential.