THE PERMEABILITY TRANSITION PORE INDUCED UNDER ANAEROBIC CONDITIONS IN MITOCHONDRIA ENERGIZED WITH ATP

The role of oxygen in the induction of mitochondrial permeability tran sitions was studied. Oxygen consumption, swelling, membrane potential and calcium transport were recorded simultaneously in isolated rat liv er mitochondria, Oxygen depletion was accomplished by saturating the m edium with Na and allowing either mitochondrial respiration or glucose /glucose oxidase to consume the residual oxygen. Upon anaerobiosis, mi tochondria were supplemented with 500 mu M ATP to support succinate-dr iven membrane potential. Under these conditions, 100 mu M Ca2+ induced cyclosporin A-sensitive permeability transitions. To eliminate the po ssible inhibition of permeability transition by high concentrations of adenine nucleotides, anaerobic mitochondria were also energized by th e combination of 20 mu M ADP and phosphoenolpyruvate/pyruvate kinase, These mitochondria also underwent Ca2+-induced permeability transition . Under both of these conditions, namely the addition of ATP as a sing le or through actions of pyruvate kinase, the respiratory components w ere totally reduced. Thus, oxygen is not a necessary factor for mitoch ondria to undergo permeability transitions. (C) 1998 Federation of Eur opean Biochemical Societies.