Objective      To compare the effects of sodium nitrite and isosorbide mononitrate on pulmonary artery pressure and pulmonary vascular remodeling in rats with high pulmonary blood flow pulmonary artery hypertension (PAH).       Methods      According to a random number table method

40 healthy male Sprague-Dawley rats were randomly assigned into 4 groups (n=10): sham operation group (group S)

PAH group (group P)

sodium nitrite 6 mg/kg group (group T1) and isosorbide mononitrate 5 mg/kg group (group T2). A left-to-right shunt PAH model was established by an arterial-venous shunt surgery created between abdominal aorta and inferior vena cava in group P

group T1 and group T2. After the rats were fed for 11 weeks

sodium nitrite (6 mg/kg) and isosorbide mononitrate (5 mg/kg) were given in group T1 and group T2

respectively

for 21 d. The same volume saline was given in group S and group P. At the end of 14 weeks

the mean arterial pressure (MAP) and mean pulmonary arterial pressure (mPAP) were monitored. The hearts were weighted to calculate right ventricular hypertrophy index (RVHI)

right ventricle mass/(left ventricle mass+septum mass) [RV/(LV+S)]

right ventricle mass/body weight (RV/BW) and left ventricle mass+septum mass/body weight [(LV+S)/BW]. The nitric oxide (NO) content in serum and lung homogenate was determined with a nitrate reductase method. The pathological change of pulmonary artery was examined with an optical microscope.       Results      Compared with group S

the mPAP

RV/(LV+S) and RV/BW of group P were increased

and the BW and serum NO content were reduced (P0.05). The pathological damage was severer in group P than in group S. Compared with group P

the mPAP

RV/(LV+S) and RV/BW were reduced in group T1 and group T2 (P0.05) and the serum NO content was increased in group T1 (P0.05) and group T2 (P0.05). Isosorbide mononitrate and sodium nitrite alleviated the pathological damage in the lung. There were no significant differences in the levels of MAP

(LV+S)/BW and the NO content in lung homogenate among the 4 groups (P0.05).       Conclusion      Long-term administration of sodium nitrite and isosorbide mononitrate improves the hemodynamics in the rats with high pulmonary blood flow PAH and attenuates pulmonary vascular remodeling induced by PAH

and the mPAP-lowering effect of isosorbide mononitrate is better than that of sodium nitrite.