Oxygen consumption rate (ṀO2 of hen eggs was measured on incubation day 16 (37.8°C, 55% humidity) during acute exposure (90 min) to ambient hyperoxia (FlO2 = 0.42) or hypoxia (FlO2 = 0.105). During the last part of these exposures, an H2 washout method was used to estimate relative changes in chorioallantoic membrane (CAM) blood flow, taking as an index the net change in the H2 washout rate constant between any experimental condition and the circulation arrested egg. Doubling normoxic FlO2 increased ṀO2 to an asymptotic value which was 4% above the normal (P < 0.05; ṀO2 in normoxia = 890 μmol/h) even after correcting for the normoxic increase in ṀO2 with time during development (ΔṀO2/Δt = 21.5 μmol/h2; P < 0.001). Halving FlO2 ralculated in the same way to 388 μmol/h. The estimate of the CAM blood flow, relative to normaxia, was 1.12 in hyperoxia (not significant, P = 0.05) and 0.68 in hypoxia (P < 0.001). The limited changes in CAM blood flow and ṀO2 during hyperoxia indicate that they are both already close to their maximal values in normoxia. During acute hypoxia the 16 day embryo behaves as an oxygen-conformer; however, the small relative decrease in ṀO2 per unit of the flow index observed during hyperoxia suggests that the embryo can regulate its CAM blood flow to a small extent. The survival of the embryo and its recovery from hypoxia without a detectable O2 repayment suggest small if any anaerobic regulatory pathways and indicate a true metabolic depression.
- Animal, chicken
- Egg metabolism, in hypoxia and hyperoxia
- Egg respiration
- Oxygen consumption, of chicken egg