Hypercholesterolemia impairs endothelium-dependent dilation in arteries. We tested the hypothesis that hypercholesterolemia impairs endothelium-dependent vasodilation by an interaction between elevated plasma lipoproteins and a presumably normal endothelium using human veins in vivo; veins do not generally develop atherosclerosis and are appropriate for testing functional alterations.Background
Methds and Resul. Full dose-response curves were constructed in 13 hypercholesterolemic and 12 normocholesterolemic subjects by infusing bradykinin (0.25 to 508 ng/min) into hand veins preconstricted with the a-adrenergic agonist phenylephrine. The maximal relaxation induced by bradykinin was 80±38%o in the controls and 103±40o in subjects with hypercholesterolemia (P=.08). Responsiveness to bradykinin was also determined after infusion of indomethacin (5.4, g/min), a cyclooxygenase inhibitor, to block the contribution of prostaglandins; maximal responsiveness was greater in hypercholesterolemic subjects (112±41%) than in controls (81±31%) (P=.03). Hypercholesterolemic subjects were more sensitive to bradykinin, with an ED5. of 4.2 ng/min versus 10.9 ng/min in controls (P=.05); a similarly increased sensitivity was found in the presence of indomethacin. The response to a maximally effective dose of nitroglycerin was greater in hypercholesterolemic subjects (142±31%o) versus 106±28% in controls (P=.007). In five hypercholesterolemic subjects, treated with lovastatin to normalize serum cholesterol concentrations, maximal responsiveness to bradykinin decreased from 103±52% to 80±28%.Conclusions
These results demonstrate that hypercholesterolemia in humans does not impair endothehlum- derived relaxing factor-mediated venodilation.