The study investigated the prooxidative in vitro effect of various Fe(2+)-EDTA concentrations on biochemical parameters of the energetic metabolism of rat liver mitochondria. Fe(2+)-EDTA was added in concentrations 150, 300 and 400 mmol/mg of mitochondrial protein. The study included the investigation of consumption of oxygen in state 4 (without ADP addition) and in state 3 (with ADP addition), and the activities of ATP-ase, superoxide dismutase (SOD) and glutathione reductase. The mitochondrial outer membrane dynamics were simultaneously monitored by the method of synchronous fluorescence fingerprint. When compared with the control group, the results imply that in state 4, the addition of 150 mmol of Fe2+/mg of mitochondrial protein caused an insignificant increase in respiration to 104%, whereas in state 3, the oxygen consumption was insignificantly inhibited to 82%. The activity of ATPase was insignificantly raised to 105%, whereas the superoxide dismutase activity has decreased significantly to 77%. The activity of glutathione reductase increased significantly to 124%. The addition of 300 mmol of Fe2+/mg of mitochondrial protein has caused a significant inhibition of oxygen consumption to 67% in state 4 and to 31% in state 3. The activity of ATPase showed an insignificant elevation to 104%. The activity of superoxide dismutase was significantly reduced to 52% and that of glutathione reductase dropped to 72%. The addition of 400 Fe2+/mg of mitochondrial protein strongly diminished the oxygen consumption to 36% in state 4, and similarly to 37% in state 3. The activity of ATP-ase was significantly decreased to 39%, the superoxide dismutase activity diminished to 17% and glutathione reductase activity dropped to 37%. The monitoring of the mitochondrial outer membrane by the analysis of synchronous fluorescence fingerprint showed that the membrane is involved in these processes. (Fig. 5, Ref. 12.)