Oxidative modification of rat cardiac mitochondrial membranes and myofibrils by hydroxyl radicals.

The effect of hydroxyl radicals generated by the FeSO4/H2O2 system on structural properties of proteins and membranes was studied in rat cardiac mitochondria and myofibrils. Exposure of mitochondria to 0.1 mmol/l FeSO4/EDTA plus 1 mmol/l H202 at 37 degrees C for 30 or 60 min caused conjugated diene formation, but it was not accompanied by accumulation of fluorescent lipid-protein conjugates. On the other hand, fluorescence measurements revealed radical-induced and time-dependent loss of tryptophans and production of bityrosines. Under the same conditions, the gradual decrease in tryptophan flurescence and increase in bityrosine formation was also observed in radical-treated myofibrils. These results suggest that *OH radicals can alter the mitochondrial and myofibrillar function via oxidation of amino acid residues and might be implicated in the pathogenesis of myocardial injury.