Endothelial cell function in patients with Down's syndrome.

Patients with Down's syndrome show an increased pulmonary vascular reactivity that could be due to an impaired vascular endothelial function, which is possibly related to increased oxidative stress. In 8 patients with Down's syndrome and 9 euploid patients of similar age, endothelium-dependent and -independent vasodilation was studied, measuring brachial flow velocity with an intravascular Doppler flow wire. Patients with Down's syndrome showed a significant impairment of endothelial function versus controls. In presence of the antioxidant vitamin C, endothelium-dependent vasodilation in the patients with Down's syndrome was only slightly, but not significantly, improved.