Studies of copper ion-induced mitochondrial swelling in vitro

1. A study of the mode and mechanism of Cu²⁺-induced mitochondrial swelling was carried out. 2. Mitochondrial swelling curves (E₅₂₀ turbidity changes) were obtained as a function of [Cu²⁺], pH, temperature and mitochondrial protein concentration. ED₅₀ was approx. 70mμmoles of Cu²⁺. Calculation of the activation energy from the Arrhenius equation gave a value of 22900cal./mole per degree with Q₁₀ 4·02. 3. No lipid peroxides were formed during swelling. 4. Changes in oxygen consumption (Clark-type electrode) were dependent on the substrate used, but revealed no increased uptake in presence of Cu²⁺. 5. Cu²⁺-induced swelling was inhibited by EDTA, 8-hydroxyquinoline, cyanide, citrate, bovine serum albumin, ATP, glutamate, GSH, dithiothreitol and sucrose. Azide, Amytal, antimycin A and oligomycin had no significant effect. Potentiation of swelling was seen with ascorbate, 2,4-dinitrophenol and succinate. 6. The occurrence of different types of mitochondrial swelling and the suggestion that Cu²⁺-induced swelling is mediated through a stoicheiometric interaction with a thiol-containing membrane receptor are discussed.