Disorders of endothelium-dependent relaxation in pulmonary disease

The pulmonary circulation is characterized by its low vascular tone at rest and its reactivity to hypoxia. Pulmonary hypertension (PH) often occurs in end-stage chronic hypoxic lung disease. Recent evidence suggests that endothelial dysfunction probably plays a key role in causing chronic hypoxic PH. In experimental conditions, exposure to hypoxia impairs endothelium-dependent relaxation of isolated pulmonary vascular rings and the release of nitric oxide (NO) from cultured pulmonary endothelial cells. In patients with chronic hypoxic PH, endothelium-dependent relaxation is impaired compared with that of control patients, whereas contractile responses to α-adrenergic agonists are significantly greater in rings from PH patients than in control rings