衰老对离体大鼠主动脉内皮依赖性血管舒张反应的影响

摘要

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( inducible nitricoxide synthase, iNOS )和内皮型一氧化氮合酶( endothelial nitricoxide synthase , 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- 4 mol/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- 4 mol/L NNLA预处理 20 min,阻断一氧化氮合酶( nitricoxide synthase , 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.③ eNOS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随增龄表达减弱,而 iNOS 随增龄表达则明显增强.%AIM:To study the effects of aging on aortic endothelium-dependent vasodilation in isolated rat aorta. METHODS:The changes of vasodilation of isolated aortic rings from 20 adult and 20 old-age rats were detected using tissue organ bath system, acetylcholine(Ach),and N-nitro-L-arginine(NNLA).The expression of inducible nitricoxide synthase(iNOS) and endothelial nitricoxide synthase (eNOS) was observed by immunocytochemistry in different age groups. RESULTS: Endothelial dependent relaxation of aortic rings(1× 10- 8, 1× 10- 7, 1× 10- 6, 1× 10- 5, and 1× 10- 4 mol/L) induced by Ach[(3.13± 0.85)% ,(12.60± 2.18)% ,(25.23± 4.63)% ,(37.73± 6.59)% ,and(50.78± 3.58)% ]in old rats obviously decreased compared with in adult rats( P< 0.01) .After 20 min pretreatment with NNLA(1× 10- 4 mol/L) to inhibit nitricoxide synthase(NOS).Ach of the same dose could not induce endothelium-dependent relaxation in the isolated aortic rings of old and adult rats.eNOS group:brown particles were seen in endothelial cell layers of adult rats,and in old rats,positive staining particles (120.524± 2.037) were weakened compared with those of adult rats.INOS group:there were fewer brown particles in endothelial cell layers of adult rats;but in old-age group there were lots of brown particles (112.371± 1.649),most of which were distributed in the media. CONCLUSION:With aging and NO decrease,endothelium-dependent relaxation declines significantly.In L-Arg-NO-pathway,abnormal expression of NOS has major effects on the synthesis of NO.The expression of eNOS weakens,and the expression of iNOS enhances with age.