ANTIOXIDANT EFFECTS OF ESTRADIOL AND 2-HYDROXYESTRADIOL ON IRON-INDUCED LIPID-PEROXIDATION OF RAT-LIVER MICROSOMES

In the present study, the antioxidant effects of estradiol (E(2)) and 2-hydroxyestradiol (2-OHE(2)) on microsomal lipid per oxidation induce d by Fe3+/ADP/NADPH and Fe2+/ascorbate are describe. The extent of lip id peroxidation was measured by thiobarbituric acid reactive substance s (TBARS) detection, low-level chemiluminescence, and oxygen consumpti on. 2-OHE, had a potent antioxidant activity, which in all cases was h igher than that of E(2). In the Fe2+/ascorbate model, 2-OHE(2) showed a similar pattern of inhibition, irrespective of the presence of NADPH or the functionality of microsomes. However, E(2) produced only a sli ght inhibition when either denatured microsomes ol native microsomes w ithout NADPH were used, whereas its protective effect increased consid erably when microsomal E(2) metabolism was favored. During enzymic Fe3 +/ADP/NADPH-induced lipid peroxidation, both E(2) and 2-OHE(2) were fo und to provide good protection. Results underline the importance of th e chemical structure of these compounds and the role of estradiol meta bolism in its antioxidant effects.