肾上腺髓质素对低氧大鼠肺动脉压的调节作用

目的　探讨肾上腺髓质素 (ADM)对肺循环的影响及低氧大鼠肺组织和血浆ADM浓度的变化。方法　将 5 0只Wistar大鼠分为对照组 (10只 )和低氧组 (40只 ) ,低氧组大鼠采用常压低氧处理 3周建立大鼠肺动脉高压模型 ;以微导管法检测大鼠平均肺动脉压 (mPAP) ,采用图像分析技术测定大鼠肺小动脉壁增厚情况 ;以放射免疫法测定大鼠肺组织及血浆ADM浓度 ;另将 30只低氧组大鼠分为 3个小组 (每组 10只 ) ,分别给予剂量为 0 5nmol/kg、1 0nmol/kg和 2 0nmol/kg的ADM静脉注射 ,观察其对大鼠肺动脉压和股动脉压的作用。结果　低氧组大鼠mPAP(30± 4 )mmHg (1mmHg =0 133kPa) ,与对照组 [(16± 3)mmHg]比较 ,差异有显著性 (P <0 0 1) ;图像分析表明 ,低氧大鼠存在明显的肺小动脉壁增厚 ;低氧组大鼠血浆ADM浓度 [(2 88± 2 4 )pg/ml]与对照组 [(16 8± 2 5 )pg/ml]比较 ,差异有显著性 (P <0 0 1) ,低氧组大鼠肺组织匀浆ADM浓度 [(2 319± 2 38)pg/g]与对照组 [(115 3± 12 7)pg/g]比较 ,差异有显著性 (P <0 0 1) ,两者均与大鼠mPAP呈正相关 (r分别 =0 5 6 7、0 6 12 ,P均 <0 0 1) ;低氧组大鼠经静脉注射ADM后 ,其肺动脉压出现显著降低 (P <0 0 1) ,维持时间为 5～ 15min ,同时其体动脉压亦有所下降 ,其效应呈

Effect of adrenomedullin on the regulation of pulmonary arterial pressure in hypoxic rats

OBJECTIVE: To evaluate the effect of adrenomedullin (ADM) on pulmonary circulation and the change of ADM in plasma and lung tissue from rats with hypoxic pulmonary hypertension. METHODS: Fifty Wistar rats were divided into the control group (10 rats) and the hypoxic group (40 rats). The animal model of pulmonary hypertension was established by exposing the rats to normobaric hypoxic conditions for 3 weeks; Mean pulmonary arterial pressure (mPAP) was measured by right cardiac catheterization, and mean systemic blood pressure (mSBP) was measured by left femoral catheterization. The thickness of pulmonary arterioles was measured by a computerized image analyser. The level of ADM in plasma and lung tissue was measured by radioimmunoassay. We ADM was administered in doses of 0.5, 1.0, 2.0 nmol/kg respectively to 30 hypoxic rats and the changes in mPAP and mSBP to ADM was evaluated. RESULTS: Rats exposed to hypoxia developed pulmonary hypertension, the mPAP in the control group being (16 +/- 3) mm Hg and in hypoxic group being (30 +/- 4) mm Hg, and the difference was significant (P < 0.01). The hypoxic rats developed significantly thickened pulmonary arterioles. The plasma level of ADM was (288 +/- 24) pg/ml in the hypoxic rats and (168 +/- 25) pg/ml in the control group the difference being significant (P < 0.01). The level of ADM in the lung homogenates from the hypoxic group was (2 319 +/- 238) pg/g and that from the control group was (1 153 +/- 127) pg/g and the difference was significant (P < 0.01). The ADM levels had a positive correlation with the mPAP (gamma = 0.567 and 0.612 P < 0.01, respectively). Administration of exogenous ADM reduced the mPAP in a dose-dependent manner in hypoxic rats, and the effect lasted 5 approximately 15 minutes. CONCLUSION: ADM has a relaxing effect on pulmonary circulation. The change of ADM in plasma and lung tissue may serve as a compensatory mechanism in maintaining the stability of pulmonary circulation in hypoxic condition.