Role of Hemoglobin Affinity and Concentration in Determining Hypoxia Tolerance of Mammals During Infancy, Hypoxia, Hyperoxia and Irradiation

The affinity of hemoglobin for oxygen is a major factor in determining the hypoxia tolerance of various species, and the increased hypoxia tolerance characteristic of infants and altitude-exposed animals. Modifications of affinity of hemoglobin, and probably hemoglobin type, occur in both young and adult animals of some species when exposed to alterations of O 2 tension or irradiation. These modifications are not dependent upon splenic activity nor changes in oxygen capacity, but may be induced by intraperitoneal injection of serum from altitude-acclimatized rats. Maximal increases in tolerance are achieved only under optimal conditions of O 2 tension, duration and frequency of exposure to hypoxia. No significant effect upon hypoxia tolerance due to alterations of O 2 capacity could be demonstrated during growth, acclimatizations or blood loss and transfusion.