Water-immersion restraint stress (WIRS), which is characterized with both psychological stress and physical stress, is widely used to induce reproducible stress ulcers in experimental animals (1). Reactive oxygen species (ROS) and nitric oxide ( • NO) generation, lipid peroxidation, and neutrophil infiltration in the gastric mucosal tissue play a critical role in the pathogenesis of WIRS-induced gastric mucosal lesions (2-5). Iwai et al. (6) have reported that, in rats with 6 h of WIRS, the level of liver lipid peroxide (LPO), which is generated via ROS, increases with concomitant increases in the levels of serum LPO and liver cell damage markers such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) activities and that pre-administration of gamazumi fruit juice or (2)-epigallocatechin gallate, each of which possesses antioxidant activity, for 2 wk attenuates all these stress-induced changes. Furthermore, the same authors have reported that not only an increase in LPO level but also decreases in superoxide dismutase (SOD) activity and reduced glutathione (GSH) level occur without changes in catalase and glutathione peroxidase activities in the liver of rats with 6 h of WIRS and that preadministration of gamazumi crude extract possessing antioxidant activity to rats with 6 h of WIRS for 2 wk attenuates the increased LPO level and the decreased SOD activity and GSH level in the liver (7). We have reported that, in the liver of rats exposed to WIRS over a 6-h period, cell damage occurs before the appearance of oxidative stress with disruption of antioxidant defense systems associated with decreased ascorbic acid (vitamin C) and GSH levels and SOD activity and enhanced lipid peroxidation, enhanced • NO generation, and neutrophil infiltration in the tissue, although the vitamin E level does not change in the liver tissue (8). We have also shown that a single pre-administration of l-ascorbic acid protects against oxidative damage in the liver of rats with 6 h of WIRS by attenuating disrupted antioxidant defense systems and enhanced lipid peroxidation, enhanced• NO generation, and neutrophil infiltration in Asaminami-ku, Hiroshima 731-0153, Japan (Received October 20, 2014) Summary We examined how dietary supplementation of vitamin E protects against liver oxidative damage in rats with water-immersion restraint stress (WIRS). Before WIRS exposure, rats received a normal diet (ND) or vitamin E-supplemented diet (VESD) (500 IU a-tocopherol/kg diet) at a mean dose of 15 g/animal/d for 4 wk. The two diet groups had serum transaminases and lactate dehydrogenase activities and adrenocorticotropic hormone, corticosterone, and glucose levels to a similar extent. VESD-fed rats had higher liver a-tocopherol concentrations and lower liver ascorbic acid, total coenzyme Q9 (CoQ9), reduced CoQ9, reduced CoQ10, and lipid peroxide (LPO) concentrations than ND-fed rats. When the two diet groups were exposed to 6 h of WIRS, the serum liver cell damage index enzyme activities incr...