Myocardial capillary angiogenesis and coronary flow in ischemia tolerance rat by adaptation to intermittent high altitude hypoxia

摘要

AIM: To determine the effects of simulated intermittent high altitude hypoxia adaptation (IHA) on coronary capillary and coronary flow (CF) in rat hearts. METHODS: Model of Langendorf-perfused isolated rat hearts were used to measure CF during ischemia-reperfusion, and immunoperoxidase staining assay and computer-aid morphometry analysis were conducted to determine the myocardial capillary densities. Cyclic GMP (cGMP) level in myocardium was measured by radio-immunoassay. RESULTS: Pre-ischemia level of CF in IHA rats was higher (IHA28 13.4 mL/min +- 1.5 mL/min, IHA42 15.4 mL/min +- 2.0 mL/min, P < 0,01) than that of normoxic rats (11.0 +- 0.8) mL/min, and the recovery of CF after ischemia-reperfusion was better in IHA rats. As an adaptive result, the myocardial capillary densities of the left ventricular myocardium in IHA rats were 1.5 times of those in normoxic control rats, but there was no apparent ventricular hypertrophy in IHA rats. Myocardial cGMP content (1.8 +- 0.7) nmol/ g in IHA rats were increased significantly compared with control rats (1.1 +- 0.4) nmol/g, but cGMP level was not altered before and after ischemia-reperfusion in either group. It was also revealed that in isolated rat hearts perfused, myocardial function recovered better in IHA rats than that in normoxic control rats. CONCLU- SION: IHA adaptation increased the tolerance of rat hearts against subsequent ischemia-reperfusion injury, and increase in coronary circulation and angiogenesis might be the mechanisms of myocardium protected by IHA.