Effect of Hypoxia on Endothelin-1 Production by Pulmonary Vascular Endothelial Cells

Endothelin-1 (ET-1), a peptide product of endothelial cells, is mitogenic for fibroblasts and smooth muscle cells. In this study we examined the effect of hypoxia on ET-1 production by bovine pulmonary vascular endothelial cells. Bovine pulmonary artery (BPAE) and microvascular endothelial (BMVE) cells were isolated, grown in tissue culture, and characterized by the presence of Factor VIII related antigen and LDL uptake. Baseline production of ET-1 by BPAE cells (measured by radioimmunoassay) increased over time. BMVE cells produced one tenth the amount of ET-1 as produced by the pulmonary artery endothelial cells under the same conditions. In both cell types, hypoxia (0% O2) significantly reduced the amount of ET-1 at 48 h. Restoration of normoxia in 21% O2 for 48 h resulted in a return of ET-1 levels to baseline. Northern blot analysis showed decreased ET-1 mRNA in cells exposed to hypoxia for 48 h. These data demonstrate that pulmonary vascular endothelial cells respond to hypoxia by reversibly decreasing ET-1 production, and this attenuation is likely regulated at the level of transcription.