Respiratory properties of blood from embryos of highland vs. lowland geese.

Respiratory properties of whole blood during development were studied in embryos of the bar-headed and Canada geese. In both species, affinity of the blood for O2 [expressed as O2 half-saturation pressure (P50)] increased with development, to a low and stable value. The low and stable P50 at pH 7.4 for the bar-headed goose, 20.1 +/- 0.3 Torr, is significantly lower than that for the Canada goose, 26.9 +/- 0.8 Torr. The data suggest a higher Bohr effect for the bar-headed goose. Hill's coefficients, buffering capacity, red cell 2,3-diphosphoglycerate, and blood hemoglobin concentrations are similar in both species. We suggest that the affinity of the whole blood for O2 is an important genetically based adaptation to ensure a high O2 content in the blood in the face of reductions in ambient PO2 associated with nesting at high altitudes. The higher Bohr effect may ensure high tissue PO2 in the presence of the high-affinity hemoglobin.