Abstract
The effect of exposure to simulated high altitude (4,500 m) on the concentration of 2,3-diphosphoglycerate (2,3-DPG) and adenosine triphosphate (ATP) in the red cell and the oxygen affinity of hemoglobin (P50) (measured at PCO2=40 mm Hg and corrected to plasma pH=7.40) was studied. It was found that a moderate physical activity is a condition for the previously reported decrease in the oxygen affinity during acclimatization to high altitude, and that this decrease is exclusively due to an increase in the concentration of 2,3-DPG in the red cell. A rapid and pronounced decrease in the extracellular concentration of inorganic phosphate was found in resting as well as exercising individuals.