DIETARY SUPPLEMENTATION WITH CAROTENOIDS - EFFECTS ON ALPHA-TOCOPHEROL LEVELS AND SUSCEPTIBILITY OF TISSUES TO OXIDATIVE STRESS

The ability of dietary supplementation with carotenoids to protect chi ck tissues against oxidative stress in vitro was examined, Male Leghor n chicks were fed on diets supplemented (100 mg supplement/kg diet) wi th either beta-carotene, zeaxanthin (beta,beta-carotene-3,3'-diol), ca nthaxanthin (beta,beta-carotene-4,4-dione) or alpha-tocopherol, or on a control diet, from 1 d old until 37 d of age, Tissues (liver, heart, skeletal muscle and plasma) were removed and assayed for total carote noids and alpha-tocopherol content and portions subjected to oxidative stress by incubation of homogenates with cumene hydroperoxide and FeS O4, Animals receiving zeaxanthin and canthaxanthin had significantly g reater carotenoid concentrations in liver, heart, muscle and plasma co mpared with untreated controls (P < 0.05); animals fed on diets supple mented with beta-carotene or alpha-tocopherol did not have significant ly different tissue carotenoid contents compared with untreated contro ls, alpha-Tocopherol supplementation elevated alpha-tocopherol levels in all tissues examined (P < 0.05), Supplementation with carotenoids d id not affect tissue alpha-tocopherol levels, but beta-carotene lowere d plasma alpha-tocopherol levels by 50% (P < 0.05), Incubation of plas ma or tissue homogenates with oxidant stressors induced lipid peroxida tion (production of thiobarbituric-acid reactive substances) in all ti ssues, Animals given alpha-tocopherol, beta-carotene or zeaxanthin had a reduced susceptibility to oxidant stress in Liver compared with uns upplemented controls (P < 0.05), and alpha-tocopherol-supplemented ani mals had reduced susceptibility in skeletal muscle compared with unsup plemented controls (P < 0.05), Canthaxanthin supplementation did not i nfluence the susceptibility to oxidant stress in any tissue examined, These results suggest that zeaxanthin, a carotenoid present in animal and human diets, may have significant activity as an antioxidant again st oxidative stress in tissues.