低氧大鼠冠状血管储备的变化及一氧化氮和内皮素-1的调节作用

目的:探讨一氧化氮和内皮素-1对低氧时冠状血管储备(CVR)变化的调节作用。方法:大鼠随机分为3组:(1)平原对照组;(2)急性低氧组;(3)慢性低氧组。分别测量心肌血流量、血浆和心肌NO₂^-、内皮素-1(ET-1)含量、心肌一氧化氮合酶(NOS)活性产并观察心肌血管结构改变。结果:(1)急性低氧导致双心室心肌血流量、心肌NO₂^-、ET-1含量、NOS活性明显增高,CVR明显下降。(2)间断低压低氧90d后,左室CVR、心肌ET-1/NO₂^-比值无明显改变;右室心肌ET-1含量、ET-1/NO₂^-比值明显增加,右室NO₂^-含量、CVR明显下降;右室冠状小血管壁增厚,管周胶原、血球压积(Hct)及右室重量指数增加。结论:急性低氧时,安静心肌血流量增加,CVR减少;慢性低氧时,右室CVR减少可能与心肌ET-1含量增加、NO含量减少、右室冠状小血管改建、Hct增高及右室肥大有关。

Changes in coronaryvascular reserve and roles of nitric oxide and endothelin-1 in regulation of coronaryvascular reserve during hypoxia

AIM:To investigate the roles of nitric oxide (NO) and endothelin-1(ET-1) in regulation of coronary vascular reserve (CVR) during hypoxia.METHODS: CVR were measured with 99m TC radiolabelled frog RBC, the changes of NO - 2,ET-1 contents, nitric oxide synthase(NOS) activity and the myocardial morphometry were observed. RESULTS: (1) Acute hypoxia caused an increase in left and right ventricular myocardial blood flow,myocardial NO - 2,ET-1 contents,NOS activity,but CVR in the left and right ventricle were decreased compared with the control group.(2) Intermittent hypobaric hypoxia for 90 days did not lead to significant change in left ventricular CVR,myocardial ET-1/NO - 2 ratio. However, right ventricular myocardial ET-1 contents,ET-1/ NO - 2 ratio were increased,right ventricular CVR and myocardial NO - 2 contents were decreased. We also observed that perivascular collagen,arterial wall thickness in right ventricle, hematocrit,RV weight index were augmented. CONCLUSION: Rest myocardial blood flow was increased,CVR was decreased;The decreased coronary vascular reserve during chronic hypoxia might be resulted from the increased hematocrit,arterial wall thickness,perivascular collagen,ET-1 content, the decreased NO content and right ventricular hypertrophy.