目的:研究增龄对离体大鼠主动脉内皮依赖性舒张的影响。方法:成年及老年大鼠各20只,利用组织器官水浴系统,通过乙酰胆碱、N-硝基左旋精氨酸,测量离体主动脉环的舒张反应变化(%)。同时利用免疫组织化学方法观察诱导型一氧化氮合酶(induciblenitricoxidesynthase,iNOS)和内皮型一氧化氮合酶(endothelialnitricoxidesynthase,eNOS)在不同年龄大鼠主动脉中的表达。结果:①老年组大鼠主动脉环对1×10-8,1×10-7,1×10-6,1×10-5,1×10-4mol/L乙酰胆碱诱发的内皮依赖舒张反应(3.13±0.85)%,(12.60±2.18)%,(25.23±4.63)%,(37.73±6.95)%,(50.78±3.58)%均较成年组明显减弱,两组之间有显著差异(P<0.01)。②离体大鼠主动脉环环经1×10-4mol/LNNLA预处理20min,阻断一氧化氮合酶(nitricoxidesynthase,NOS)后,同样剂量的乙酰胆碱不再诱发上述内皮依赖性舒血管反应。③eNOS组:在老年组血管内膜层可见棕褐色的阳性反应颗粒120.524±2.037,但较成年组相比,可发现阳性反应明显减弱。iNOS组:成年组内膜及中膜层可见较弱的棕褐色阳性反应颗粒沉在老年组(112.371±1.64),阳性反应明显增强。结论:随增龄,血管内皮分泌的一氧化氮逐渐减少,导致血管内皮依赖性舒张减弱;NOS的异常表达对一氧化氮减少起着重要的作用,eNOS随增龄 Objective: To study the effect of aging on the endothelium-dependent relaxation of isolated aorta in rats. Methods: 20 adult and aged rats were used to measure the change of relaxation (%) of isolated aortic rings by acetylcholine and N-nitro-L-arginine using tissue and organ water bath system. Immunohistochemistry was used to observe the expression of inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) in the aorta of rats of different ages. Results: ① In the aged group, the aortic rings induced endothelium-dependent relaxation induced by acetylcholine (1 × 10-8, 1 × 10-7, 1 × 10-6, 1 × 10-5, 1 × 10-4mol / L) 3.13 ± 0.85%, 12.60 ± 2.18%, 25.23 ± 4.63%, 37.73 ± 6.95%, 50.78 ± 3.58%, respectively, which were significantly lower than those in the adult group (P < 0.01). ② The isolated aortic rings were pretreated with 1 × 10-4 mol / LNNLA for 20 min, and nitric oxide synthase (NOS) was blocked after the same dose of acetylcholine did not induce the endothelium-dependent vasorelaxation. ③eNOS group: In the elderly group of vascular intima visible brown positive reaction particles 120.524 ± 2.037, but compared with the adult group, we found that the positive reaction was significantly weakened. In the iNOS group, weaker sepia-positive particles in the intima and media of the adult group were found in the elderly group (112.371 ± 1.64), and the positive reaction was significantly enhanced. CONCLUSION: The nitric oxide secreted by the vascular endothelium decreases gradually with age, leading to a decrease of endothelium-dependent relaxation. Aberrant expression of NOS plays an important role in the reduction of nitric oxide. With increasing age