低氧习服过程中大鼠心脏的适应性改变

Adaptive changes in heart during acclimation to hypoxia in the rat

目的 :观察在低氧习服过程中 ,大鼠心肌毛细血管密度、血流供应和心脏功能的变化规律。方法 :大鼠在 5 0 0 0m模拟高原低氧 5、15d和 30d后 ,用碱性磷酸酶 (ALP)组织化学方法显示心肌毛细血管并进行图象分析 ;用放射性微球法测定心肌血流量 ;用心导管技术测定左、右心室功能。结果 :在低氧习服过程中 ,整个右室心肌血流量显著增加 ,功能显著增强。低氧 15d后 ,右室心肌毛细血管密度虽无明显变化 ,但单位面积内毛细血管数与肌纤维数的比值 (C/M)显著增高。低氧 5d时左室心肌血流量虽显著增加 ,但左室功能明显降低 ;随着低氧时间的延长 ,左室心肌血流量和左室功能恢复正常。在低氧 30d时 ,左室心肌毛细血管密度和C/M比值均显著增高。结论 :大鼠在对低氧习服过程中 ,右室心肌血流量持续增加、心肌肥大并伴有毛细血管增生及功能增强 ;左室先有心肌血流量增多和心功能降低 ,后来心肌血流量恢复并出现毛细血管增生 ,同时左室功能恢复。

AIM: To study the changes in myocardial blood flow (MBF), capillarization and cardiac function in the rat during acclimation to hypoxia. METHODS: Myocardial capillary density (CD) and capillary/myocyte ratio (C/M) was assayed by alkaline phosphatase histochemistry. Biomicrosphere method was used to determine MBF in the rat after 5, 15 or 30 days hypobaric hypoxic exposure (5 000 m). RESULTS: In the course of hypoxia, MBF and cardiac function increased in the right ventricle. However, in the left ventricle, acute hypoxia caused an increase in MBF and a decrease in cardiac function. Both returned to the control level on continued hypoxic exposure. Neovascularization occurred after 15 day or 30 day of hypoxic exposure in both ventricles, judged from the significant increment of C/M ratio albeit the CD remained unchanged in the right ventricle. CONCLUSION: Our findings indicate that adaptive changes in rat heart during acclimation to hypoxia include: ① persistent increase in MBF, hypertrophy associated with increase in capillarity and enhanced cardiac function of the right ventricle; ② increase in MBF and depression of cardiac function at first, then followed by recovery of MBF and increase in capillarity accompanied with recovery of left ventricular function.