Endothelin-1 (ET-1) is a potent vasoconstrictor peptide produced by vascular endothelial cells and is believed to play an important role in the pathophysiology of the pulmonary vasculature. We have investigated the early changes in ET-1 plasma levels in lung transplant recipients at various intervals before and after isolated lung transplantation. The mean plasma ET-1 level immediately before transplantation was 0.8 +/- 0.1 pg/ml. This was significantly increased to 2.6 +/- 0.5 pg/ml shortly after unclamping and vascular reperfusion of the allograft, and remained high 4 h (2.3 +/- 0.5 pg/ml), 6 h (2.4 +/- 0.6 pg/ml), and 12 h (1.7 +/- 0.3 pg/ml) after transplantation. Thereafter, the level of ET-1 started to decline, reaching 1.3 +/- 0.3 pg/ml 24 h and 0.9 +/- 0.3 pg/ml 1 week after transplantation. This early increase in ET-1 plasma level is consistent with our observation of alterations in pulmonary vascular resistance, pulmonary artery pressure and cardiac output early after transplantation. These findings demonstrate that an increase in plasma ET-1 levels shortly after lung transplantation may have a detrimental effect during the postoperative course early after transplantation.