Abstract: Objective To investigate the effects and mechanisms of adrenomedullin (ADM) and adrenomedullin receptor (ADMR) on hypoxia pulmonary hypertension (HPH) in rats.Method Eighteen male Wistar rats were randomly divided into three groups:control group and hypoxic group, hypoxic with ADM group .ADM was subcutaneously administered into rats with ADM by osmotic minipump（1.5μg·kg-1·h-1）.After 21d ,The Mean pulmonary arterial pressure (mPAP),right ventricular hypertrophy index(RV/(LV+S)) were measured and hypoxic pulmonary vascular remodeling(HPSR) were observed with morphometric analysis. The levels of pulmonary arterial plasma ADM were measured by radioimmunoassay. The semiquantitate in situ hybridization was used to measure the expression of ADMR mRNA in pulmonary artery walls. Result (1) The level of mPAP, RV/(LV+S) ,the ratio of vascular wall thick ness to external diameter(MT%) and ratio of vascular wall area to total area (MA%) were significantly higher on hypoxia group than those in (2) The pulmonary artery plasma ADM level was significantly higher in hypoxic group and hypoxic with ADM group than that in control group (P<0.01), and the ADM level decreased in rat of hypoxic with ADM group compared with hypoxic group(P<0.05).(3) ADMR mRNA expressed higher in pulmonary artery walls of hypoxia group and hypoxic with ADM group（P<0.01）.Conclusion ADM subcutaneously administered may partly prevent the development of HPH and pulmonary vascular remodling. Exogenous ADM had no negative feedback on pulmonary arterial plasma ADM and ADMR mRNA.