EDN1 and Chuvash polycythemia: While we could not detect up-regulation of other HIF-target genes in iron-deficient PASMCs, this result is entirely consistent with the previous finding that ET-1 was the only HIF-target gene (among 10 targets tested) that increased in the lungs of mice with Chuvash polycythemia which have a moderate normoxic HIF accumulation (35).