POTENTIATION OF IRON-INDUCED LIPID-PEROXIDATION BY A SERIES OF BIPYRIDYLS IN RELATION TO THEIR ABILITY TO REDUCE IRON

We determine the relative abilities of three bipyridyls (Paraquat P++, Benzylviologen B++ and Diquat D++) to stimulate iron-induced lipid pe roxidation in relation to their ability to redox cycle and to reduce i ron. The ability to redox cycle increases with the redox potential, in the order: P++ < B++ < D++. The initial rates of Fe3+ reduction incre ased from P++ to D++ and B++. NADPH-dependent microsomal lipid peroxid ation was measured in different conditions (1) increasing incubation t ime, 100 mu M bipyridyl, 10 mu M FeCl2; (2) increasing concentrations of bipyridyls, 10 mu M FeCl3, 10 min incubation time; (3) increasing c oncentrations of FeCl3, 100 mu M bipyridyl, 10 min incubation time. Bi pyridyls potentiated the production of malondialdehyde (MDA), particul arly with the shortest incubation times and the lowest concentrations of FeCl3, in the order of activity P++ < D++ < B++. The strong correla tion between the initial rate of lipid peroxidation and Fe3+ reduction indicates that the rate of Fe3+ reduction determines the intensity of the potentiation effect of bipyridyls on lipid peroxidation-on the co ndition that the amount of peroxidizable substrate is not the limiting factor. (C) 1997 Elsevier Science Ireland Ltd.