This study shows some aspects of endothelial function closely related with cardiac surgery: 1) Following global myocardial ischemia and reperfusion, the coronary endothelium has an impaired ability to express endothelium-dependent vasodilation to the receptor-dependent agonists while endothelium-dependent relaxation to the receptor-independent A23187 and phospholipase C is unaltered. The relaxation to sodium fluoride, which acts on a pertussis toxin-sensitive G-protein is impaired. These experiments indicate that impaired receptor-mediated production of EDRF/NO following reperfusion injury could be due to G-protein dysfunction in the pathway which links endothelial cell receptors to the pathway of EDRF/NO synthesis; 2) Forty-five minutes of cardioplegic arrest of the canine heart does not alter the production EDRF/NO in the epicardial coronary artery. Similar experiments support the concept that UW solution is safe for cardiac preservation during heart transplantation; 3) In coronary, renal, femoral and pulmonary arterial segments, protamine induced endothelium-dependent vasodilation mediated by the stimulated release of EDRF/NO. In the pulmonary circulation, differently of the coronary, renal and femoral arteries, protamine-induced endothelium-dependent vasodilation could be inhibited by comparable amounts of heparin, and this effect was overcome by adding additional protamine; 4)ln 83% of the superfusion experiments, effluent from the left IMA induced greater relaxation of the bioassay ring than did the right IMA due to the basal release of EDRF/NO. Because EDRF/NO induces vasodilation and also inhibits platelet adhesion, platelet aggregation, and atherogenesis, luminal release of EDRF/NO by the IMA could contribute to superior results when the artery is used in bypass grafting. Upon exposure of the grafts to hypoxia, the vasodilator activity of effluent from both IMA and saphenous vein grafts was augmented.This hypoxic augmentation could be inhibited by indomethacin treatment and the relaxation was quickly reversed with return to normoxia.
vascular endothelium; nitric oxide; EDRF