Effects of estrogen replacement on oxidative stress induced by psychological stress in ovariectomized rats

Abstract

We examined whether acute psychological stress enhances plasma oxidative stress, which is restored by estrogen replacement in ovariectomized rats using nitrotyrosine (NT) as a stress marker. Female Wistar rats aged 9 wk were ovariectomized and treated with placebo or 17β-estradiol (1.5 mg/60-day release, sc) pellets 4 wk after ovariectomy. Rats aged 16 wk were catheterized for blood sampling. Six days post-surgery, rats were exposed to cage-switch or restraint stress and blood samples were collected during the stress and the recovery from the stress. Basal plasma NT level was significantly higher in the placebo-treated rats than in the estrogen-treated rats, though the basal plasma nitric oxide metabolites (NOx) level was similar in both groups. The cage-switch stress significantly increased the plasma NT concentrations, and decreased the NOx levels during the stress and the recovery only in the placebo-treated rats. The stress had no effects on the plasma NT and NOx levels in the estrogen-treated rats. These results suggest that estrogen replacement attenuates the excess oxidative stress and restores NO bioavailability during the psychological stress and the recovery. [J Physiol Sci. 2008;58 Suppl:S107]