Pii: S1095-6433(02)00009-0

Chicken embryos were chronically exposed to hypoxia ( ;110 mmHg) during development, and assessed for PO2 detrimental metabolic and morphological effects. Eggs were incubated in one of four groups: control (i.e. 151 mmHg), or treated with continuous 110 mmHg (15% O ) during days 1–6 (H1–6), 6–12 (H6–12), or 12–18 (H12–18) with 2 normoxia during the remaining incubation. Metabolism ( ), body mass, hemoglobin (Hb) and hematocrit (Hct) were VO2 measured in embryos on days 12 and 18 of incubation and in day-old hatchlings. Ability to maintain was acutely VO2 measured during a step-wise decrease in from normoxia to hypoxia (55 mmHg). On day 12, of H1–6 eggs P V O O 2 2 were significantly lower than in the control and H6–12 eggs. P in H6–12 eggs was lower than in control and H1–6 crit eggs. Body mass of H1–6 and H6–12 embryos on day 12 was significantly lower than in control embryos, while in H6–12 embryos, Hct and Hb were higher. On day 18, H6–12 embryos had significantly lower than control eggs. VO2 Body mass of H6–12 and H12–18 embryos was significantly lower than control embryos. Hct and Hb did not differ between treatments. In hatchlings, mass, Hb and Hct had returned to values statistically identical to controls. However, H6–12 embryos had significantly lower . Long-term hypoxia altered when hypoxic incubation occurred during V V O O 2 2 the middle third of incubation, but not during earlier or later incubation. Thus, chronic hypoxic exposure during critical periods in development altered the developmental physiological trajectories and modified the phenotypes of the developing embryos. 2002 Elsevier Science Inc. All rights reserved.