Treatment of dilute suspensions of rat liver mitochondria with Fe²⁺ results in the formation of lipid peroxides, an extensive fall in turbidity, and the loss of 65% of the mitochondrial protein and 39% of the mitochondrial lipid into the suspending medium. These changes occur with little alteration in the number or size of the mitochondrial particles. The formation of mitochondrial membrane
... [Show full abstract] ghosts is suggested.
Membrane ghosts prepared from mitochondrial by Fe²⁺-induced peroxidation are found to retain almost no pyridine nucleotides, 33% of the total flavin, 50% of the ubiquinone, and 66%, 60%, and 27%, respectively, of the cytochromes a, b, and c + c1 of the mitochondria. An additional 67% of the initial cytochrome c + c1 is recovered from the supernatant medium following removal of the membrane ghosts by centrifugation.
The membrane ghosts rapidly oxidize succinate, glutamate, and 3-hydroxybutyrate in the presence of added nicotinamide adenine dinucleotide and cytochrome c. They show an antimycin A-insensitive NADH-cytochrome c reductase activity.
Fe²⁺-induced lipid peroxidation results in inactivation of all of the mitochondrial isocitrate dehydrogenase activity, 80% of the 3-hydroxybutyrate dehydrogenase, 36% of the malate dehydrogenase, and 23% of the succinate dehydrogenase. There is no loss of glutamate dehydrogenase activity. However, 96% of the glutamate dehydrogenase and 57% of the malate dehydrogenase are released into the soluble fraction.
Membrane ghosts prepared with Fe²⁺ exhibit no respiratory control or coupled phosphorylation with any of the substrates tested. There is an active Mg²⁺-dependent adenosine triphosphatase which is not stimulated by the addition of 2,4-dinitrophenol.
