Iron loading modifies the fatty acid composition of cultured rat myocardial cells and liposomal vesicles: effect of ascorbate and alpha-tocopherol on myocardial lipid peroxidation.

Increased generation of free radicals and accelerated lipid peroxidation are important manifestations of iron toxicity. We have studied the effect of iron loading on lipid peroxidation in cultured rat myocardial cells by direct measurement of the fatty acid composition of cellular lipids. Iron loading produced by 24-hour incubation of cultured cells with 0.36 mmol/L ferric ammonium citrate resulted in a moderate reduction in polyunsaturated fatty acids (PUFAs) such as 22:5 and 22:6. A more drastic reduction in PUFAs and an apparent reciprocal increase in the proportion of saturated fatty acids were both obtained after 24 hours of incubation of liposomal vesicles prepared from whole cell lipid extracts with iron at between pH 4.5 and pH 5.5. Reduction of 22:5 and 22:6 was first noticed at 3 hours, and undetectable levels were reached by 12 and 24 hours of incubation. Ascorbate had a biphasic effect on liposomal PUFA levels: at low concentrations (0.057 mmol/L) it enhanced the iron-induced changes in liposomal fatty acid composition, but at higher concentrations (0.57 and 5.7 mmol/L), it inhibited these changes. Unlike ascorbate, alpha-tocopherol (0.023 to 2.3 mmol/L) inhibited the iron-induced reduction in PUFAs in a dose-dependent manner, with complete inhibition of the iron effect at 2.3 mmol/L. These observations underline the particular sensitivity of PUFAs to iron-induced lipid peroxidation. They also illustrate the ability of ascorbate and alpha-tocopherol to modify iron-induced lipid peroxidation. Further studies are required to explore the possible therapeutic implications of these observations in clinical iron overload.