Abstract： Objective To investigate the change and significance of inducible nitric oxide synthase (iNOS) and intersititial cells of Cajal (ICC) in the small intestine of rats with postoperative ileus (POI).Methods Thirty healthy adult Wistar rats were randomly divided into the control group ( 15 rats) and POI group ( 15 rats) according to the random number table.The gastrointestinal transit rates of the 2 groups were detected.The distributions and expressions of iNOS and c-kit in the small intestines of the rats in the 2 groups were detected by immunohistochemical staining,and the mRNA expressions of c-kit and iNOS were examined by quantitative real-time polymerase chain reaction (qRT-PCR).All data were analyzed by the t test.Results Two rats in the POI group died of excessive dosage of anaesthesia or hypothermia,and the remaining 13 rats in the POI group were included in the analysis.The gastrointestinal transit rate was 42％ ± 14％ in the POI group,which was significantly lower than 64％ ± 13％ in the control group ( t =6.56,P ＜ 0.05 ).The results of immunohistochemical staining showed that the number of cells with c-kit positive staining was 8.9 ± 2.9,which was significantly smaller than 14.4 ± 5.0 in the control group ( t =3.97,P ＜ 0.05 ).The number of cells with iNOS immune-positive reaction increased to 13.6 ±4.9,while there was nearly no cells with iNOS immune-positive reaction in the control group.The results of qRT-PCR showed that the relative mRNA expressions of c-kit and iNOS were 1.6 ± 0.8 and 2.2 ± 1.2 in the POI group,and 2.6 ± 1.1,0.5 ± 0.5 in the control group.There were significant differences on the mRNA expressions of c-kit and iNOS between the POI group and the control group ( t =2.86,4.61,P ＜ 0.05).Conclusions ICC reduction and iNOS increase are observed in rats with POI.The change of the 2 factors may plav an important role in the mechanisms of POI.