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pubmed:abstractText |
In this study, we investigated the hemodynamic effects and receptor-blocking properties of the nonselective endothelin antagonist bosentan in pigs during normoxia and acute hypoxia. Hypoxic pulmonary hypertension was induced by decreasing the fraction of inhaled oxygen to 0.1. In a control group of pigs, hemodynamic parameters proved to be stable through 2 hours of hypoxia. Infusions of endothelin-1, endothelin-3, and sarafotoxin 6c into the pulmonary artery resulted in pulmonary and systemic vasoconstriction during normoxia, whereas endothelin administration during hypoxic pulmonary hypertension resulted in pulmonary vasodilation. After administration of bosentan, the vasopressor effect of endothelin-1 during normoxia was significantly attenuated and the pulmonary vasodilatory effect of endothelin-1 during hypoxia was reduced. Furthermore, the development of hypoxic pulmonary hypertension was significantly reduced by bosentan. In contrast, bosentan did not influence the pulmonary vasopressor response to the thromboxane mimic U-46619. We therefore conclude that vasopressor endothelin receptors seem to be activated by endogenous endothelin released during hypoxia, leading to an increase in the pulmonary vascular tone.
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