Effects of increased left ventricular work, hypoxia, or coronary ligation on hearts from rats at high altitude

Isolated perfused hearts from rats acclimatized to Jungfraujoch (altitude 3454 m) were less resistant to the effects of high levels of heart work or mild hypoxia than hearts from litter mates reared at Geneva (340 m). However, in response to coronary artery ligation hearts from acclimatized rats were better able to maintain tissue contents of adenosine triphosphate, phosphocreatine and glycogen. A projected explanation for the increased biochemical resistance to ischaemia was a relative increase in the coronary flow rate. The data support the hypothesis that exposure to high altitude helps to protect the heart against coronary occlusion by an increased resistance developing as a result of increased sensitivity to high levels of heart work and hypoxia.