Periodate-oxidized ATP stimulates the permeability transition of rat liver mitochondria

Periodate-oxidized ADP (oADP)2 and periodate-oxidized ATP (oATP) stimulate the permeability transition in energized rat liver mitochondria measured as the Ca2+-efflux induced by Ca2+ and Pi. In the presence of Mg2+ and Pi, mitochondria lose intramitochondrial adenine nucleotides at a slow rate. oATP induces a strong decrease of the matrix adenine nucleotides which is inhibited by carboxyatractyloside. Under these conditions, Mg2+ prevents the opening of the permeability transition pore. EGTA prevents the Pi-induced slow efflux of adenine nucleotides, but is without effect on the oATP-induced strong decrease of adenine nucleotides. This oATP-induced strong adenine nucleotide efflux is inhibited by ADP. oATP reduces the increase of matrix adenine nucleotides occurring when the mitochondria are incubated with Mg2+ and ATP. This effect of oATP is also prevented by carboxyatractyloside. oATP is not taken up by the mitochondria. It is suggested that oATP induces a strong efflux of matrix adenine nucleotides by the interaction with the ADP/ATP carrier from the cytosolic side. The induction of the mitochondrial permeability transition by oADP and oATP is attributed to two mechanisms-a strong decrease in the intramitochondrial adenine nucleotide content, especially that of ADP, and a stabilization of the c-conformation of the ADP/ATP carrier.