Paraquat potentiates iron-induced microsomal lipid peroxidation: modulation by the diet lipid composition

SUMMARY

The study concerns the role of two combined factors—lipid composition of the microsomal membranes and the iron concentration in the incubation medium—in lipid peroxidation catalysed by paraquat (P⁺⁺). Rats were subjected to diets containing 5% lipids composed of either tripalmitin (T), peanut oil/rapeseed oil (v/v) (C) or fish oil (F). The level of polyunsaturated fatty acids in the microsomal membranes was higher in C and F than in T. The level of vitamin E was lowest in F. The activity of the system ‘Cyt P450-NADPH cyt c reductase’ increased in the order T<C<F. The iron concentrations initiating a basal NADPH-dependent lipid peroxidation have been established. p⁺⁺ potentiates this peroxidation due to additional reduction of Fe³⁺ by p^+., rather than by O₂^.- as is usually thought to occur. The sensitivity of the membranes to the potentiating effect of P^{+ +} is mainly determined by a high level of polyunsaturated fatty acids, but also by a low level of the antioxidant vitamin E.