SUPERIOR AND DISTINCT ANTIOXIDANT EFFECTS OF SELECTED ESTROGEN METABOLITES ON LIPID-PEROXIDATION

The effect of the estrogen metabolites, 4-hydroxyestrone and 17 alpha- dihydroequilin (metabolites of estradiol-17 beta and equilin, respecti vely), were examined for antioxidant effects on plasma and lipoprotein lipid peroxidation. Lipid peroxidation was evaluated by products of b oth fatty acid (thiobarbituric acid-reactive substances [TBARS]) and c holesterol (oxysterols) oxidation from lipoproteins or whole plasma. A lthough all estrogens significantly reduced lipid peroxidation, 4-hydr oxyestrone was far more potent than either equilin or 17 alpha-dihydro equilin in inhibiting TBARS formation in lipoproteins induced by Cu2+. Similar effects were also noted on TBARS formation in THP-I macrophag es in culture, However, 17 alpha-dihydroequilin (along with equilin) s trongly inhibited oxysterol formation, whereas 4-hydroxyestrone was in effective. These studies suggest that different estrogens might act pr eferentially on distinct lipid substrates in exhibiting antioxidant ef fects. (C) 1996 by W.B. Saunders Company