Figure 1.

(A) Representative original tracing showing the response of an isolated 19‐d chicken embryo caudomedial intrapulmonary artery to 15 min of hypoxia followed by reoxygenation. Hypoxia was induced by switching the gas mixture aerating the organ bath from 21% O₂‐74% N₂‐5% CO₂ (Po₂~19.2 kPa) to 95% N₂‐5% CO₂ (Po₂~2.5 kPa). (B) Response to hypoxia of pulmonary artery rings from 19‐day chicken embryos exposed to in ovo acute hypoxia‐reoxygenation. Eggs were exposed to 10% O₂ for 30 min followed by 15 min of reoxygenation with 21% O₂ (HypOx‐NormOx group) or 80% O₂ (HypOx‐HyperOx). A group of eggs was maintained at 21% O₂ for 45 min (NormOx‐NormOx) and a group of eggs was maintained at 21% 0₂ for 30 min and then exposed to 80% O₂ for 15 min (NormOx‐HyperOx group).Results are shown as mean ± SE of measurements in 6–9 embryos.