EFFECTS OF ALPHA-TOCOPHEROL AND BETA-CAROTENE ON HEPATIC LIPID-PEROXIDATION AND BLOOD-LIPIDS IN RATS WITH DIETARY IRON OVERLOAD

The ability of dietary antioxidants to reduce lipid peroxidation induc ed by ir on overload was examined in weanling male Sprague-Dawley rats . Animals were fed ad libitum a modified AIN-76A diet (control) or con trol diet with 0.5% alpha-tocopherol acid succinate, 0.5% crystalline trans-beta-carotene, or 0.5% alpha-tocopherol acid succinate + 0.5% tr ans-beta-carotene for four weeks. In the following four-week period, t he animals received the above diets with 10,000 mu g Fe/g; a control g roup continued to receive 35 mu g Fe/g, and a high-iron group received 10,000 mu g Fe/g with no antioxidants. After four weeks of dietary su pplementation with alpha-tocopherol, beta-carotene, or alpha-tocophero l + beta-carotene, liver concentrations of alpha-tocopherol and beta-c arotene increased significantly (p < 0.001). Liver lipid peroxidation, measured by the lipid-conjugated diene assay, increased significantly from 0.012 mu mol/mg of lipid in the controls to 0.021 mu mol/mg of l ipid in animals receiving the high-iron diet. However, lipid peroxidat ion was significantly reduced in all animals fed the antioxidants, wit h the group fed alpha-tocopherol + beta-carotene having a lower level than the high-iron group. Total serum cholesterol was elevated in anim als fed a high-iron diet and in animals fed the high-iron diet with al pha-tocopherol. In contrast, total serum cholesterol levels in the two groups of animals receiving the diets containing high iron with beta- carotene alone or high iron with beta-carotene + alpha-tocopherol were significantly reduced to the level of the control group. High-density lipoprotein cholesterol also decreased to baseline in the animals rec eiving beta-carotene alone. Modulation of lipid peroxidation by alpha- tocopherol or beta-carotene may be an important mechanism for reducing oxidative stress.