DZIALOWSKI, E.*; VON PLETTENBERG, D.; ELMONOUFY, N.; BURGGREN, W.: Chronic Hypoxic Effects on Metabolism and Hematology in Developing Chicken Embryos

Chicken embryos wereexposed to chronic hypoxia (PO₂ ~ 131 mmHg) during development, and assessed for detrimental metabolic effects and the ability to repair them. Eggs were incubated in one of four groups: untreated (i.e. 155 mmHg), or treated with continuous 15% hypoxia during days 1-6 (D1-6), 6-12 (D6-12), or 12-18 (D12-18) with normoxia during the remaining incubation. Metabolism (VO₂), body mass, hemoglobin (Hb), and hematocrit (Hct) were measured in eggs on days 12 and 18 and in hatchlings. Ability to maintain VO₂ was measured acutely during a step-wise decrease in PO₂ from normoxia to hypoxia (55 mmHg). At day 12, VO₂ from D1-6 and D6-12 populations was significantly lower than untreated eggs. Pcrit in D6-12 eggs was lower than in untreated and D1-6 eggs. Body mass of day 12 embryos in hypoxia from D6-12 was significantly lower than in untreated embryos, while Hct and Hb were higher. On day 18, D6-12 eggs had VO₂ significantly lower than untreated eggs. Body masses of D6-12 and D12-18 eggs were significantly smaller than untreated eggs. Hct and Hb did not differ between treatments. In hatchlings, VO₂, mass, Hb, and Hct were similar among treatments. However, D1-6 and D12-18 eggs produced hatchlings with lower Pcrits than untreated eggs or D6-12 hypoxia exposed eggs. Long term effects of hypoxia on VO₂ and mass occurred in D6-12 embryos. Differences in VO₂ and mass between untreated eggs and D6-12 eggs were observed on day 12 and 18, but disappeared upon hatching. Chronic hypoxic exposure during critical periods in development alters the developmental physiological trajectories and modifies the phenotypes of developing embryos.