Electron spin resonance (ESR) spectroscopy and spin trapping agent PBN were applied to measure directly the changes of oxygen free redicals (OFR) in gastric mucosa of rats with portal hypertension (PHT) injured by shockreperfusion, and treated with superoxide dismutase (SOD), radix salviae miltiorrhizae (RSM), with concomitant monitoring activity of SOD and pathology of gastric mucosa. Results showed that the amount of OFR increased markedly in gastric mucosa of PHT rats during the shock-reperfusion. The pathological changes were in accordance with alteration of the amount of OFR and the activity of SOD. Gastric mucosa in PHT was more susceptible to shock-reperfusion insult than normal controls. The anti-oxidant SOD, RSM used at early stage exerted mild gastric mucosal insult through different mechanisms.
