| Summary: | We examined the oxygen dependence of mitochondrial respiration in the high altitude bar‐headed goose and several low altitude waterfowl species (greylag goose, barnacle goose, and mallard duck). Mitochondria were isolated from the flight muscle and their respiration was measured by high‐resolution respirometry at avian body temperature (41°C), with malate/pyruvate or malate/pyruvate/succinate fuel combinations. Mitochondria were well coupled with high phosphorylation efficiencies in all birds. Respiratory capacities, cytochrome oxidase excess capacity, and uncoupled respiration rates were all similar between species. Oxygen kinetics depended on respiration state, as half‐maximal mitochondrial respiration occurred at O 2 tensions (P 50 ) of 0.1‐0.2 Torr in State 4 (no ADP) and 0.8‐0.9 Torr in State 3 (maximal ADP). These data suggest that intramyocellular O 2 tension could regulate mitochondrial respiration during flight, particularly at high altitude where O 2 supply is reduced. (Supported by NSERC of Canada)
|
|---|