Reactive Nitrogen Species Contribute to the Rapid Onset of Redox Changes Induced by Acute Immobilization Stress in Rats

Acute stress leads to the rapid secretion of glucocorticoids, which accelerates cellular metabolism, resulting in increased reactive oxygen and nitrogen species generation. Although the nitrergic system has been implicated in numerous stress-related diseases, the time course and extent of nitrosative changes during acute stress have not been characterized. Outbred male Wistar rats were randomly allocated into control (n = 9) or 120 min acute immobilization stress (n = 9) groups. Serial blood samples were collected at 0 (baseline), 60, 90, and 120 min. Plasma corticosterone concentrations increased by approximately 350% at 60, 90, and 120 (p<0.001) min of stress. The production of nitric oxide, measured as the benzotriazole form of 4-amino-5-methylamino-2',7'-difluorofluorescein, increased during stress exposure by approximately 5%, 10%, and 15% at 60 (p<0.05), 90 (p<0.01) and 120 (p<0.001) min, respectively, compared to controls. Nitric oxide metabolism, measured as the stable metabolites nitrite and nitrate, showed a 40-60% increase at 60, 90, and 120 (p<0.001) min of stress. The oxidative status of 2',7'-dichlorofluorescein in plasma was significantly elevated at 60 (p<0.01), 90, and 120 (p<0.001) min. A delayed decrease of approximately 25% in the glutathione redox ratio at 120 min (p<0.001) also indicates stress-induced cellular oxidative stress. The peroxidation of plasma lipids increased by approximately 10% at 90 (p<0.05) and 15% at 120 (p<0.001) min, indicative of oxidative damage. It was concluded that a single episode of stress causes early and marked changes of both oxidative and nitrosative status sufficient to induce oxidative damage in peripheral tissues.