Portal circulation was reduced to 50-60% for one hour by partial occlusion of the superior mesenteric artery for the purpose of studying the relationship between reperfusion injury, bacterial translocation and multiple system organ failure. Forty dogs were divided randomly into four groups, and 1 x 10(10)/kg E. coli O111B4 were fed to each animal 12 hours before operation. Group I constituted the controls, in which sham operations were performed. The experimental procedure was completed in all the animals of the other three groups. Rubia yunnanensis, an anti-oxidant, was given to group III. Amikacin was given to group IV. The results showed that group II was characterized by bacteremia, hypoxemia, and hypotension as compared with group I. The levels of superoxide dismutase (SOD) in the whole blood were markedly lowered and malondialdehyde (MDA) values significantly elevated in group II after reperfusion compared with group I. Plasma levels of anaphylatoxin C5a and B2 (TXB2) were significantly raised in group II beginning with the reperfusion when compared with groups I, III and IV. Pathological changes in the intestine, liver and lung were remarkable only in group II, including acute necrosis of the intestinal mucosa, granulocyte infiltration, hemorrhage and edema of the lung, degenerative changes of myocardial and hepatic cells, and bacterial invasion of the blood, liver and lung. These results suggested that bowel ischemia and reperfusion may promote gut barrier failure and bacterial translocation, then contribute to the development to multiple system organ failure (MSOF) by allowing bacteria or endotoxin normally contained within the gut to reach the portal and systemic circulations where it fuels the septic process. Oxygen free radicals, anaphylatoxin and thromboxane may be potential factors in the development of gut barrier failure and MSOF.