Early damage of vascular endothelium during cardiac ischaemia.

To determine the site of reperfusion damage after ischaemia the leakage of xanthine dehydrogenase and xanthine oxidase was assessed in vascular and interstitial effluents. Contractile function was reduced during hypoperfusion but improved after the addition of superoxide dismutase and vasoxin to the perfusion medium. Both interstitial fluid and coronary effluent showed dehydrogenase and oxidase activity after no flow ischaemia. Furthermore, the ratio of lactate dehydrogenase to creatine kinase in coronary effluents was reduced. These findings indicate that the myocardial interstitium may be a site of ischaemic membrane damage since this space contains hypoxanthine and xanthine oxidase. The protective effect of superoxide dismustase also indicates the possibility of damage due to oxygen derived radicals in the cardiac interstitium during low flow perfusion.