Pulmonary hypertension is characterized by an increase in vascular tone of an abnormal proliferation of muscle cells in the wall of small pulmonary arteries. Endothelin-1(ET-1) is a potent endothelium-derived vasoconstrictor peptide with important mitogenic properties. It has been recognized that endothelin-1 may contribute to increase in pulmonary arterial tone or smooth muscle proliferation in congenital heart disease patients with pulmonary hypertension. To explore the role of endothelin-1 in patent ductus arterious, we measured endothelin-1 before and after closure of ductus in artery and vein plasma.

Seven patients of patent ductus arteriosus underwent thoracoscopic clipping of dustus in 1997 June-August. Their age was 1-24 months and male 4, female 3. Blood samples were drawn from radial artery and inferior vena cava before, 30 minutes and 90 minutes after closure of ductus. Endiothelin-1 was measured by radioimmunoassay method.

Arterial endothelin-1 was 17.96±8.09pg/ml at before closure of ductus, 13.47±3.14pg/ml at 30 minutes after closure of ductus and 11.43±2.9pg/ml at 90 minutes after closure of ductus. Venous endothelin-1 was 9.34±3.55pg/ml at before closure, 8.9±3.74pg/ml at 30 minutes after closure and 8.4±3.71pg/ml at 90minutes after closure of ductus. Arterial endo-thelin-1 was significantly higher than venous one at before and 30 minutes after ductus closure(p<0.05). Arterial endothelin-1 at 90 minutes after ductus closure was significantly lower than that at before the closure(p<0.05).

Patients pf patent ductus arteriosus have substantial alterations in plasma endo-thelin-1 which is decreased after closure of ductus. Comparing with venous plasma, the higher levels of ET-1 in arterial plasma suggest pulmonary production of endothelin-1, which may contribute to induce pulmonary hypertension.