Various studies have clearly demonstrated that green tea catechins possess potent antioxidative properties, and the preventive effects against various oxidative diseases have been reported. The aim of this study was to investigate the effect of green tea extract on the tissue injury caused by ischemia/reperfusion (I/R) of the gut. I/R injury of the intestine was caused by clamping both the superior mesenteric artery and the celiac trunk for 45 min followed by release of the clamp allowing reperfusion for 1 h or 4 h. This procedure results in splanchnic artery occlusion (SAO) shock. Rats subjected to SAO developed a significant fall in mean arterial blood pressure, and only 10% of the animals survived for the entire 4-h reperfusion period. Surviving animals were sacrificed for histological examination and biochemical studies. Rats subjected to SAO displayed a significant increase in tissue myeloperoxidase (MPO) activity and malondialdehyde (MDA) levels, significant increases in plasma tumor necrosis factor (TNF)-alpha levels and marked injury to the distal ileum. Increased immunoreactivity to nitrotyrosine was observed in the ileum of rats subjected to SAO. Staining of sections of the ileum obtained from SAO rats with anti-intercellular adhesion molecule (ICAM-1) antibody and with anti-P-selectin antibody resulted in diffuse staining. Administration of green tea extract (20 and 10 mg kg(-1) i.v.) 15 min prior to the onset of gut reperfusion significantly reduced in a dose-dependent manner the fall in mean arterial blood pressure, the mortality rate, infiltration of the reperfused intestine with polymorphonuclear neutrophils (MPO activity), lipid peroxidation (MDA levels), production of TNF-alpha, and histological evidence of gut injury. Administration of green tea extract also markedly reduced nitrotyrosine formation and the up-regulation of ICAM-1 and P-selectin during reperfusion. In order to clarify that green tea extract might be useful in the therapy of I/R injury, we also investigated the effect of green tea extract (20 mg kg(-1) i.v.) when administered 5 min after the onset of gut reperfusion. Similar to the pretreatment approach, the post-treatment also significantly reduced the gut injury induced by I/R. These results demonstrate that green tea extract significantly reduces I/R injury of the intestine.