Pulmonary hypoxia increases endothelin-1 gene expression in sheep.

The hypoxic pulmonary vasoconstrictor response (HPVR) is a physiologic mechanism for directing pulmonary blood flow to nonhypoxic regions of the lung. The mechanism of this response remains unclear. To investigate the role of endothelin-1 (ET-1), a potent vasoconstrictor produced by vascular endothelium, in HPVR an in vivo model of alveolar hypoxia was developed. When one lung in an anesthetized sheep was made hypoxic, the static ET-1 mRNA levels in lung tissue increased in proportion to the observed decrease in pulmonary blood flow (Qp) to that lung. With reversal of hypoxia, Qp and ET-1 levels returned to baseline. This relationship between alveolar hypoxia and ET-1 mRNA levels suggests a role for ET-1 in the local pulmonary response to hypoxia.