17Beta-estradiol protects against quinolinic acid-induced lipid peroxidation in the rat brain.

The neurotoxin quinolinic acid has been identified as a causative agent in Huntington's disease and is a metabolite of the tryptophan pathway in the brain. In the present study, the in vivo and in vitro effect of 17beta-estradiol on lipid peroxidation induced by quinolinic acid was investigated. For the in vivo experiments ovariectomized female rats were administered with 100 microg 17beta-estradiol daily for seven days prior to and seven days following the intrahippocampal injection of 1 micromol quinolinic acid. The level of lipid peroxidation in brain homogenate was investigated using the thiobarbituric acid test. The in vitro experiments were performed in brain homogenates of ovariectomized female rats. The homogenate was treated with quinolinic acid alone or in combination with 17beta-estradiol. Quinolinic acid increased lipid peroxidation in a dose dependent manner in vitro, while homogenate co-treated with 17beta-estradiol showed a significant reduction in lipid peroxidation. 17Beta-estradiol was also shown to be protective against quinolinic acid in vivo. These results could explain the neuroprotective effect of 17beta-estradiol.