Objective To investigate the effects of angelica solution on chronic hypoxic pulmonary hypertension in rats.Methods Thirty SD rats were randomized into normoxic group,hypoxic group and angelica solution-protected group.The model of rat chronic hypoxic pulmonary hypertension was made by method of isobaric hypoxia.Angelica solution were injected before hypoxia,while the other two groups were injected normal saline.After 28d of hypoxia,pulmonary artery pressure were measured.Expressions of proliferating cell nuclear antigen (PCNA) and inducible nitric oxide synthase (iNOS) in pulmonary artery were detected by immunohistochemical staining.The index of wall thickness of rat pulmonary arteriole-percentage of the wall area in the total vascular area(wA%) were measured by a computerized image analyzer.Results The mean pulmonary artery pressure (mPAP) of normoxic group,hypoxic group and angelica solution-protected group were10.50±1.90,35.36±9.11,18.32±2.30 (mm Hg);wA% of the three groups were 52.71±5.16,82.38±8.43,64.58±9.54 (%),mPAP and wA% were significantly higher in the hypoxic group than those in the normoxic group (P<0.01) and angelica solution-protected group (P<0.01).PCNA expression of normoxic group,hypoxic group and angelica solution-protected group were 3.15±1.10,24.50±5.72,12.67±3.46 (%).The PCNA expression in the pulmonary artery was significantly higher in the hypoxic group than those in the normoxic group (P<0.01) and in the angelica solution-protected group (P<0.01).iNOS expression of normoxic group,hypoxic group and angelica solution-protected group were 2.13±1.01,17.33±3.53,37.50±7.04 (%).iNOS expression in the pulmonary artery was higher in the hypoxic group than those in normoxic group (P<0.01),and angelica significantly increased iNOS expression in comparison with the normoxic and hypoxic groups (P<0.01).Conclusion Angelica solution alleviates chronically hypoxia induced pulmonary hypertension in rats by inhibiting the espression of PCNA in pulmonary artery and up-regulating the expression of iNOS.