Objective:To study the pathogenetic mechanism of intestinal injury in the aged rat with pneumonia and the effect of Dusuqing(毒素清) on it.Methods:The models of rats with Escherihia coli pneumonia were duplicated and divided into aged control group(ACG),aged model group(AMG),high doses group(HDG) and low doses group(LDG) of Dusuqing and norfloxacin group.The pathological changes in lung tissue and intestine,the contents of intestinal 6-keto-prostaglandim F1α(6-keto-PGF1α),thromboxane B2(TXB2),nitride oxide(NO),malondialdehyle(MDA) and the activity of superoxide dismutase(SOD) were observed.Results:The lung and intestinal injury in AMG was more serious.The decrease of SOD activity and 6-keto-PGF1α content,the increase of content of TXB2,NO,MDA in the AMG were more significant than those in the ACG.In comparison with those in the AMG,the level of SOD activity,6-keto-PGF1α content were increased,otherwise the contents of MDA and NO were decreased in the HDG,the LDG and the norfloxacin group.Conclusions:The injury mediated by prostaglands and free radical is related to the occurance and development of damage of intestinal tissue with pneumonia. Dusuqing is able to improve this damage obviously in aged rats with pneumonia and the mechanisms and regulation of prostaglands metabolism.