ESTROGENS INHIBIT COPPER AND NON-TRANSITION METAL-MEDIATED OXIDATION OF LOW-DENSITY-LIPOPROTEIN

Estrogens have been shown to have an inhibitory effect on copper and c ell-mediated oxidation of low density lipoprotein (LDL) in vitro. We r eport that estradiol is also effective in inhibiting LDL oxidation med iated by the azo compounds APH [2,2'-azobis-(2-aminidinopropane hydroc hloride)] and AMVN [2,2'-azobis-(2,4-dimethyl-valeronitrile)]. These c ompounds thermally decompose to produce peroxyl radicals, and their ac tion does not depend on the presence of either transition metals or pr eformed lipid peroxides. In addition to acting directly as chain-break ing antioxidants, it has been suggested that estrogens may act like as corbate to recycle tocopherol from the tocopheryl radical. However, we have demonstrated that unlike ascorbate, estradiol does not have the ability to recycle either tocopherol or beta-carotene during the lag p hase of copper oxidation, but behaves in this respect more like the li pid-phase chain-breaking antioxidant probucol.