Estimation of the Rate of CO₂ Diffusion Into the Red Cell Through the Bohr Shift

Abstract

When the reactions of the red blood cell with O₂ and CO₂ are observed in a reaction chamber of a micro-photometric apparatus, the plasma layer around the cell tends to be superfluously thick and usually becomes highly resistive to the O₂ and CO₂ diffusions. Nevertheless, since the diffusivity of CO₂ through aqueous solution, in general, is about 20 times as high as that of O₂, the rates of the Bohr-on- and off-shifts have been thought to be almost the same as those of the oxygenation and deoxygenation. In our observation, however, the Bohr-on-shift was constantly slower than the oxygenation, while the Bohr-off-shift was comparable with the deoxygenation rate. The half-time of the Bohr-on-shift was about 60% longer than that of the oxygenation. This fact suggested that the diffusion rates of CO₂ and/or HCO₃ ions were comparable with that of O₂ and they could even be evaluated quantitatively by comparing the Bohr-shifts with the oxygenation and deoxygenation rates. Thus, in the present study the estimation of the CO₂ diffusion rate into and out of the red cell was attempted from the measured rates of the simple O₂ reactions and the Bohr shift.