Biphasic release of immunoreactive endothelins following acute pulmonary thromboembolism in pigs

The purpose of this investigation was to study the role of endothelins (ETs ) in the pathogenesis of acute pulmonary thromboembolism (PTE). Eighteen pi glets (20 +/- 3 kg) were anesthetized and ventilated with 100% oxygen, five of them then served as controls. Acute thromboembolic injury in the lung w as induced by injecting 15-25 ml of preformed clots into the left lower lob ar pulmonary artery during thoracotomy. Pulmonary arterial pressure (Ppa) i ncreased by at least 2.5-fold from baseline. During the subsequent 8 h, sev en blood samples were collected from the left atrium and assayed for immuno reactive ETs. The results showed that following PTE: (1) Ppa remained eleva ted but cardiac output remained constant throughout the experiments; (2) pl asma level of immunoreactive ETs increased in the embolized group compared to controls and the profile of immunoreactive ET release suggested a biphas ic response. We conclude that the release of these vasocontractile and bron choconstrictive mediators after PTE may contribute to ventilation perfusion mismatching and account for the pulmonary hypertension and deterioration o f gas exchange that are often seen clinically.