title: Modulation of growth and metabolism of the chick embryo by a brief (72-hr) change in oxygen availability.
abstract: Growth of the chick embryo is accelerated by brief (72-hr) exposure to 60% O2 beginning on day 16 of incubation, and acute (2-3 hr) hyperoxia stimulates oxygen consumption (VO2). However, the increment in VO2 that accompanies acute exposure to 60% O2 is only about half that required to account for the degree of growth acceleration observed during 72 hr of hyperoxia. We tested the hypothesis that the magnitude of the oxygen-induced change in embryonic metabolism depends on the length of exposure by making daily measurements of embryonic VO2 during brief (72-hr) exposure to 60% or 15% O2. White leghorn eggs were incubated in 21% O2 for 15 days. On day 16 the experimental eggs were switched to 60% or 15% O2; control eggs were maintained in 21% O2. Oxygen consumption and CO2 production (VCO2) were measured daily. Embryo and organ weights were compared on day 18. Wet and dry weights of briefly hyperoxic embryos were significantly greater than those of normoxic controls. The relative increase in wet weight was significant for the heart and liver but not the brain. Oxygen consumption increased 7% relative to control after 24 hr of hyperoxia and 17% after 72 hr; VO2/gm embryo was 9% greater than control on day 18. Normal growth deceleration was exaggerated by hypoxia; mean wet and dry weights of the briefly hypoxic embryos were significantly less than those of controls. Organ wet weights also showed growth retardation, although the relative decrease in brain weight was not significant. Body water concentration increased in briefly hypoxic embryos. Oxygen consumption was 13% less than control after 24 hr and 17% less after 72 hr.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D002642:Chick Embryo / Q000254:growth & development* / Q000378:metabolism; D010101:Oxygen Consumption
chemical_list: D002245:Carbon Dioxide