FE2+ VITAMIN-C - AN APPROPRIATE IN-VITRO MODEL SYSTEM TO INITIATE LIPID-PEROXIDATION/

The Fe2+/vitamin C system has often been used to initiate in vitro lip id peroxidation. In this paper, we attempt to locate the optimal condi tions of the Fe2+/vitamin C system to be used in lipid peroxidation ex periments. We have measured the quantity of lipid peroxidation through assessment of thiobarbituric acid reactive substances. We tested the influence of the Fe2+ and vitamin C concentration, the pH, the reactio n temperature, and different buffer systems on the extent of lipid per oxidation in preparations of pig heart membranes. The optimum rate of lipid peroxidation occurred at an Fe2+/vitamin C ratio of 1:5. Decreas ing pH and changing the buffer system resulted in changes of the exten t of peroxidation. We also show that the EPR spin trap technique with 5,5-dimethyl-pyrroline-1-oxide (DMPO), which is used to detect free ra dicals in the Fe2+/vitamin C system, cannot work. This is because vita min C immediately quenches the formed DMPO adducts by reduction. In ad dition, no evidence was found as to the nature of Fe2+/vitamin C forme d radicals in experiments using superoxide dismutase, catalase or mann itol, butylhydroxyanisol, and alpha-tocopherole as radical scavengers.