ABSTRACT
ObjectiveTo investigate the role of iNOS in the middle and late stage of pulmonary hypertension (PH) and the effect of L-Arginine(L-Arg) on these stage.MethodsThirty healthy male SD rats were randomly divided into five groups.All rats except those in control group were injected intraperitoneally (ip) with a single dose (50 mg/kg) of MCT to induce PH.Then the L3 and L5 groups were injected ip with 500 mg/kg L-Arg daily for 3 weeks and 5weeks respectively,the M3 and M5groups received a daily ip injection of the same amount of saline as L-Arg for 3 weeks and 5 weeks respectively; the same amount of saline was injected ip daily in control group for 5 weeks.Right ventricular systolic pressure(RVSP) was measured before lungs were excised for immunohistochemistry at the end of experiments. ResultsThe expressions of iNOS and elastin in M3 and M5 were higher compared to the control group,but L-Arg partly reduced the expressions of iNOS and elastin both at 3weeks and 5 weeks post-MCT.The reduction of eNOS expression in L3 and L5 groups were lower compared to M3 and M5 groups,but the eNOS expression in L3 and L5 groups were still lower than control group.ConclusionDuring the middle and late stage of PH,the expression of eNOS was decreased.The expression of iNOS was induced,which would produce numerous NO.However,these NO had no benefit on the development of PH.L-Arg could restore the balance of eNOS and iNOS,and could inhibit the development of PH,which may provide a new clues to explore the pathogenesis and treatment of PH.