Objective. Whether chronic hypoxia attenuates myocardial ischemia-reperfusion injury remains controversial because confl icting data have been reported probably due to the existence of many factors infl uencing the functional recovery of hearts. These factors include the differences of species, the time at which hypoxia begins, the degree of hypoxia, and so on. Regarding chronic hypoxia from birth, so far the only available data are based on fi ndings in rabbit hearts. The purpose of this study was to describe the effect of chronic hypoxia from birth on myocardial reperfusion injury in the rat heart. Methods. Normoxic hearts were obtained from rats housed in ambient air for 6 weeks (normoxic group); hypoxic hearts were obtained from rats housed in a hypoxic chamber (13%-14% oxygen) from birth for 6 weeks (hypoxic group). Isolated, crystalloid perfused working hearts were subjected to 30 min of global normothermic ischemia followed by 15 min of reperfusion; functional recovery was then measured in the two groups. The excretion of cyclic guanosine monophosphate (cGMP) in the coronary drainage was measured at the end of the preischemia and reperfusion periods. Results. The percent recovery of the left ventricular developed pressure and the fi rst derivative of left ventricular pressure were signifi cantly better in the hypoxic group than in the normoxic group. cGMP excretion in the coronary drainage was signifi cantly increased during both the preischemia and reperfusion periods. Conclusion. Chronic hypoxia from birth increased myocardial tolerance to ischemia-reperfusion injury with increased cGMP synthesis in the isolated heart model in rats.
- Congenital heart defect
- Guanosine monophosphate
- Myocardial reperfusion injury
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine
- Cardiology and Cardiovascular Medicine