Influences of exercise and endurance training on the oxygen dissociation curve of blood underin vivo andin vitro conditions

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Abstract
In experiments with graded exercise of 15 men (6 untrained, 3 semitrained, 6 endurance-trained) the trained subjects showed a massive shift to the right of thein vivo O2 dissociation curve (ODC) of femoral venous blood. At a saturation of 20 to 25% (18 mkp/sec)PO2 was about 9 mm Hg higher for the trained than for the untrained group. The following factors play a role: 1. The 2,3-diphosphoglycerate [2,3-DPG] concentration was increased by 15 to 20% in the trained group which explains about 2 mm Hg of the difference inPO2. 2. Exercise acidosis in the femoral venous blood depends to a large extent on CO2 in the trained, but on lactic acid in the untrained group. At low saturations the CO2-Bohr effect increases sharply thus having a greater importance in the trained subjects. This factor can explain about 2 mm Hg of the difference. However, influence of chloride and 2,3-DPG on the Bohr effect must be taken into consideration. 3. Since the large ODC-shift to the right of the trained group was not reproducible underin vitro conditions, it is suggested that a rapidly decaying unknown substance accounts for the remaining difference inPO2.

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