Myocardial capillary angiogenesis and coronary flow in ischemia tolerance rat by adaptation to intermittent high altitude hypoxia.
Abstract
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.
CONCLUSION: 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.
Keywords:
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.
CONCLUSION: 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.