Plasma endothelin-1 level in chronic obstructive pulmonary disease: relationship with natriuretic peptide.

Background and Objective: Endothelin-l (ET-1) is a potent vasoconstrictor peptide produced by the vascular endothelium. The purpose of this study was to elucidate the pathophysiological role of ET-1 in patients with pulmonary hypertension secondary to chronic obstructive pulmonary disease (COPD). Method We measured plasma ET-1 levels during right heart catheterization both at rest and during exercise on room air and while breathing oxygen in patients with COPD. In addition, we simultaneously measured plasma levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). Results: Plasma ET-l levels at rest were significantly higher in 21 patients with COPD than in 16 control subjects (p < 0.001). For COPD patients, there was no correlation between the plasma ET-1 level and pulmonary arterial pressure or pulmonary vascular resistance at rest. On the other hand, there was a significant negative correlation between plasma ET-1 level and mixed venous oxygen tension (r = -0.503, p < 0.05). Also, the plasma ET-1 level was positively correlated with those of ANP (r = 0.540, p < 0.05) and BNP (r = 0.533, p < 0.05) at baseline. Oxygen administration significantly decreased plasma ET-1 levels at rest (p < 0.05). Plasma ET-1 levels did not change significantly with exercise despite the progression of pulmonary hypertension and hypoxemia. In contrast, plasma ANP and BNP levels both increased markedly with exercise (p < 0.01). Conclusion: We conclude that in patients with COPD, the plasma ET-1 level is not affected by acute progression of pulmonary hypertension and hypoxemia during exercise, and persistent hypoxemia may be associated with an increase in the plasma ET-1 level. In addition, our findings suggest that ANP and BNP may modulate the pulmonary vascular tone by interacting with ET-1 in these patients.