Change in PCO2 in red cell suspension following bicarbonate shift

To reveal the CO2 diffusion process into and out of the red blood cell (RBC), changes in PCO, following the HCO3- shift were examined. The RBC suspension was mixed at 37 degrees C with saline solution having different HCO3- concentrations. In proportion to the intracellular HCO3- change caused by the HCO3- shift, the PCO2 change was increased. The rate of change increased as the hematocrit and the initial intracellular HCO3- content decreased. For calculating the above PCO2 change, a theoretical equation was derived from the Henderson-Hasselbalch equation and the relation between both the changes in buffer base and intracellular pH. The calculated PCO2 change coincided well with the measured value, suggesting the validity of the theoretical equations.