Adaptation of hemoglobin function to subterranean life in the mole, talpa europaea

In order to understand the mechanism responsible for the high oxygen affinity of mole blood, we investigated in the mole, Talpa europea, red cell parameters that determine hemoglobin function. We have found that the oxygen half saturation pressure (P₅₀) of mole blood is 2.85 kPa (21.4 Torr) at pCO₂ 4.7 kPa, pH 7.4 and 37°C. The concentration of 2,3-diphosphoglycerate (2,3-DPG) averaged 5,3 mmol/l in red cells. In addition, we have determined P₅₀ in hemoglobin solutions at various concentrations of 2,3-DPG at an assumed intraerythrocytic pH of 7.2 and 37°C. These data were used to calculate the association constants of 2,3-DPG to mole hemoglobin. P₅₀ was 1.89 kPa (14,2 Torr) in hemoglobin solutions without 2,3-DPG. The response to 2,3-DPG was relatively low. Noteworthy, CO₂ did not affect the oxygen affinity at constant pH in the presence of 2,3-DPG. Our results suggest that the high blod oxygen affinity of the mole can be atributed to a weak interaction of its hemoglobin with 2,3-DPG.