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目的 阐明模拟微重力因素对肺循环局部调节功能的影响。 方法 采用尾部悬吊大鼠模型模拟微重力效应，制备离体动脉环测定肺动脉对几种血管活性物质的反应性变化。 结果 与对照组相比，尾部悬吊7 d内皮完整组大鼠肺动脉对氯化钾（10～70 mmol/L）的收缩反应无显著性变化，对苯肾上腺素（10-9～10-5 mol/L）的收缩反应明显降低，对乙酰胆碱（10-9～10-5 mol/L）的舒张反应增强，对卡托普利（10-5～3×10-3 mol/L）的舒张反应无明显变化。尾部悬吊7 d去内皮组大鼠肺动脉对氯化钾、苯肾上腺素、硝普钠的反应性较对照组无明显变化。 结论 尾部悬吊7 d引起大鼠肺动脉内皮细胞释放一氧化氮（NO）增加，肺动脉舒张功能增强“,”Objective To clarify the effects of simulated microgravity on the local regulating function of the pulmonary circulation. Method Rat tail-suspension(TS) was used as the animal model to simulate the effects of microgravity.The changes in responses of pulmonary artery to several vasoactive agents were determined by using in vitro vessel rings perfusion technique. Result As for the endothelium-intact vessel rings from TS group compared with those from the control(C) group,the contractile responses of pulmonary artery to potassium chloride (KCl,10～70 mmol/L) did not change obviously after 7 d tail-suspension,which were markedly diminished as to phenylephrine (PE,10-9～10-5mol/L).The vasodilatory responses to acetylcholine (ACh,10-9～10-5mol/L) were markedly enhanced,which did not change obviously as to captopril (Cap,10-5～3×10-3 mol/L).The vasoreactivity of endothelium-removed pulmonary artery rings to all vasoactive agents did not change after 7 d tail-suspension as compared with those from control rats. Conclusion The release of nitric oxide (NO) by rat pulmonary arterial endothelium was enhanced after 7 d tail-suspension.The vasodilatory function of pulmonary artery was enhanced.