The effect of estrogen on nitric oxide content and nitric oxide synthase activity in hypoxic pulmonary hypertensive rats

Objective To investigate the effect of 17-β estradiol on nitric oxide content and nitric oxide synthase activity in hypoxic pulmonary hypertensive rats.Methods The animal model of pulmonary hypertension was established by exposing the rats to normabaric hypoxic conditions for 3 weeks.Eighteen male SD rats were randomly divided into three groups:control group,E_(2) preventive group,hypoxic group.The mean pulmonary artery pressure(mPAP) was examined by right cardiac catheterization,and the right ventricle(RV) and left ventricle plus septum(LV + S) of rat were weighed respectively,and the RV/(LV + S) was calculated.Lung specimens were examined by light microscope and morphological analysis semiquantitatively.The WT%(ratio of vascular wall thickness/vascular external diameter) and WA%(ratio of vascular wall area/total vascular area) were measured by a computerized image analyzer.NO and NOS activity in the plasma and lung tissue were measured via spectrophotometer.Results In the hypoxic group,mPAP,the RV/(LV + S),WT% and WA% increased significantly compared with those in the control group(all P 0.01).In the preventive group,the mPAP,the RV/(LV + S),WT% and WA% decreased remarkably compared with those in hypoxic group(all P 0.01).In the hypoxic group,NO and NOS activity in the plasma and lung tissue were markedly decreased in comparison with control group(all P 0.05).In the E_(2) preventive group,NO and NOS activity in the plasma and lung tissue were higher than those in the hypoxic group,respectively(all P 0.05).Conclusion It is suggested that 17-β estradiol can partly reduce pulmonary arterial remodeling by increasing concentration of NO and NOS activity.