Production of VEGF, but not sVEGFR-1, is inhibited in HIF-α^−/− macrophages. (A) HIF-1α and HIF-2α expression was assessed by real-time PCR in bone marrow–derived macrophages from HIF-1α^flox/flox/LysMcre mice or HIF-1α^flox/flox control mice. (B) Bone marrow–derived macrophages from HIF-1α^flox/flox/LysMcre mice (HIF-1α^−/− macrophages) or from HIF-1α^flox/flox control mice (HIF-1α^+/+ macrophages) were left untreated or were stimulated with 100 ng/mL GM-CSF, at ambient O₂ or at 0.5% O₂. Cell-free culture supernatants were assessed for sVEGFR-1 (B) after 48 hours. (C) VEGF levels from the same supernatants as in panel B. Cells were also assessed for levels of sVEGFR-1 (D) and VEGF (E) transcript by real-time PCR. Data are mean ± SEM of 8 mice per group.