Rate of the Bohr shift in human red cell suspensions

¹ Department of Physiology, Graduate School of Medicine, and Department of Anesthesiology, Schools of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania

We have measured the rate at which the O₂ tension rises in a partially oxygenated suspension of normal human red cells at 37 C as a result of a sudden rise in CO₂ tension (the Bohr shift) in a Hartridge-Roughton rapid reaction apparatus. A Teflon covered platinum electrode was used to measure O₂ tension. The rise in O₂ tension had an average half time of 0.12 sec following increments of 18–65 mm Hg in CO₂ tension in twelve experiments on the blood of three normal individuals. The comparable movement of O₂ out of the red cell as a result of a decrease in ambient O₂ tension at a constant CO₂ tension had an average half time of 0.012 sec in four experiments on the blood from the same three subjects. This suggests that the velocities of the reactions of CO₂ are rate-limiting in the Bohr shift. Acetazolamide (10^–3 m) slowed the rate of the Bohr shift to less than one-seventh; no measurable change in O₂ tension occurred until about 0.03 sec.