Abstract: AIM: To compare the effects of ambrisentan and bosentan on right ventricle remodeling in rats with hypoxic pulmonary hypertension(HPH).METHODS: Forty Sprague Dawley rats were randomly divided into five groups: control group,model group,ambrisentan group,bosentan group and placebo group(eight rats in each group).Rats in the control group were kept under normal environment for 4 weeks while rats in the other groups were kept in hypobaric hypoxia environment(8 h/day) for 4 weeks.For bosentan group,ambrisentan group and placebo group,bosentan(125 mg/kg),ambrisentan(5 mg/kg) and normal saline(2 ml) were given at the third week,respectively.At the end of 4 weeks,mean pulmonary arterial pressure(mPAP) and right ventricular systolic pressure(RVSP) were determined.RV/(LV+S) and the weight ratio of right ventricle weight vs.body weight(RW/BW) were calculated.The right ventricle tissues were Masson stained to observe the degree of myocardial fibrosis and in H/E to observe the pathological changes.RESULTS: Compared with those in the model group and the placebo group,mPAP,RVSP,RV/(LV+S),RW/BW and CVF in ambrisentan group and bosentan group were significantly reduced,with no statistically significant difference in the observed indexes between ambrisentan group and bosentan group.H/E staining revealed that the degree of myocardial hypertrophy significantly attenuated in ambrisentan group and bosentan group compared with that in model and placebo groups.CONCLUSION: Ambrisentan and bosentan effectively decreases pulmonary artery pressure and restrains right ventricular hypertrophy and myocardial fibrosis in rats with HPH.There is no significant difference in the effects of ambrisentan and bosentan on right ventricle remodeling in rats with HPH.