Acute effects of estradiol and of diethylstilbestrol: Pro- or antioxidant potential?

This study was aimed to examine the effects of a single high dose of natural and synthetic estrogens on the antioxidant defense enzymes in liver and blood. Female Wistar albino rats, four to six months old, were divided into three groups, and received either i.p. injections of diethylstilbestrol (DES; 150 mg kg(-1) b.w.) or s.c. injections of estradiol (E-2; 25 mg kg(-1) b.w.), and the third group (control) was injected the solvent. Animals were killed under light ether anesthesia three hours after injection. Cu-Zn superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (Cat) enzyme activities and fluorometric malondialdehyde (MDA) determination were performed in liver tissue homogenates and in blood. Acute estradiol injection caused a significant increase in both MDA levels and GPx activity in liver tissue when compared to the controls, (p < 0.05 and p < 0.02; respectively). Changes in both enzyme activities and MDA concentration were unremarkable following acute DES injection. In blood, only Cu-Zn SOD activity was significantly altered in blood following E-2 injection. Although the significance of alteration in GPx activity remains unclear, it is most likely related to enhanced generation of lipoperoxides. A significant increase in MDA concentrations in liver tissue is indicative of pro-oxidative damage rather than an antioxidant action by E-2

Coadministration of melatonin and estradiol in rats: Effects on oxidant status

This study was designed to investigate the effects of melatonin and estradiol (E2) on lipid peroxidation and antioxidant defense enzymes in blood and liver tissue when administered in vivo. Wistar albino rats were divided into three experimental groups and treated with either estradiol (25 mg/kg bw, s.c.), melatonin (i. p.), or melatonin plus E2, whereas control animals had diluent injections only. Melatonin was given 10 mg/kg bw x 2 intraperitoneally 30 min before and 60 min after E2 treatment to the melatonin plus E2 group. Animals were sacrificed three hours after the estradiol injection, and their blood and liver tissues were prepared for biochemical analyses. Tissue malondialdehyde (MDA) levels and antioxidant enzyme activities superoxide dismutase (SOD) and glutathione peroxidase (GPx) - were determined in the postmitochondrial fraction, and the results were compared. Estradiol injection caused significant increases in both MDA levels and GPx activity in liver. When melatonin was administered in combination with E2, the effect of estradiol on MDA levels was abolished. A significant decrement in SOD activity occurred in melatonin-treated animals. GPx activity in the blood of E2 plus melatonin-injected animals was significantly higher than those in control animals. Melatonin-treated animals exhibited relatively lower levels of SOD activity than those from the control and E2 plus melatonin groups. This indicates that estradiol could exert oxidant action resulting in an increment in tissue malondialdehyde levels. Enhanced activity of GPx in both liver and blood following melatonin injection may indicate the contribution of this neurohormone on the antioxidant defense