The expression of endothelial nitric oxide synthase traffic inducer (NOSTRIN) in the placenta of the patients with pregnancy induced hypertension (PIH) was detected and its role in the pathogenesis of PIH was studied. The pathological changes in placental vessels were observed by HE staining. NO2-/NO3-, the stable metabolic end products of NO, was measured with nitrate reductase. The eNOS activity in placental tissues was assayed by spectrophotometry. Western blot analysis was applied to detect NOSTRIN expression. The incidence of thickening and fibronoid necrosis of placental vessels was significantly higher in women with PIH than in the normal group (P < 0.01). The levels of placental NO2-/NO3- in PIH patients (27.53 +/- 7.48 micromol/mg) were significantly lower than in normal group (54.27 +/- 9.53 micromol/mg, P < 0.01). The activity of eNOS was significantly decreased in PIH group (12.826 +/- 3.61 U/mg) as compared with that in normal group (21.72 +/- 3.83 U/mg, P < 0.01). Western blot analysis revealed that both groups expressed 58 kD NOSTRIN, but the protein level was significantly higher in women with PIH than in the normal group (P < 0.01). A significant negative correlation existed between the expression of NOSTRIN protein and the activity of eNOS in placental tissue of women with PIH (r = -0.57, P < 0.01). It was concluded that the level of NOSTRIN expression in placenta of women with PIH was increased, which may play an important role in the pathogenesis of PIH.