Studies of lipid peroxidation in isolated rat heart mitochondria.

: Peroxidation in isolated, functionally intact rat heart mitochondria was induced by iron/ascorbate or ADP-iron/NAD(P)H. Compared to liver mitochondria, MDA formation was very low and lipohydroperoxides not detected. The NADPH-mediated peroxidation which generally resulted in somewhat higher MDA levels was accompanied by an increasing inhibition of ADP-stimulated respiration. The active respiration was sensitively inhibited at very early stages of MDA formation, whereas in the same period the CAT-insensitive respiration exhibited almost no response at all. It was demonstrated that the decrease in active respiration correlated with the time for half-maximum MDA formation. No considerable degradation of major mitochondrial phospholipids was observed during two hours of incubation. It was not until after complete inhibition of respiration and onset of enhanced MDA formation that cardiolipin, phosphatidylethanolamine and, later, phosphatidylcholine were diminished.