Effects of Inhibition of RBC

experiments were performed at 37°C. Rates of CO2 excretion were determined by measuring the fraction of CO2 in mixed expired gas in a steady state. The time-course of extracellular pH equilibration in the effluent perfusate was measured in a downstream stopflow pH electrode apparatus. CO2 excretion was reduced by 16% when the lungs were perfused with suspensions containing erythrocytes whose HCO3 / Clexchange rate was inhibited, compared with CO2 excretion when the lungs were perfused with normal erythrocyte suspensions. A fall of 0.06 in effluent perfusate extracellular pH was noted during perfusion with inhibited erythrocyte suspensions, in contrast to no observable downstream pH change during perfusion with normal erythrocyte suspensions. These results are in close agreement with the predictions of a theoretical model. Our observations suggest that CO2 transfer in capillary beds will be adversely affected in vivo when the rate of the erythrocyte HCO-/ Clexchange is abnormally low. Since a number of commonly used drugs are known to inhibit the chloride shift in human erythrocytes, these findings may have important clinical implications, especially in patients with impaired lung function.