Abstract

Carbon dioxide transport in blood involves both the red cells and the plasma, with constant interchange of water, and chloride and bicarbonate ions, across the cell membrane. It also involves mutual interactions between CO2 and oxygen uptake and release, first clearly defined by C. Bohr and J. S. Haldane et al. In the decade after 1920, L. J. Henderson, D. D. Van Slyke and their colleagues achieved a quantitative description of equilibrium for CO2 and bicarbonate transport during the respiratory cycle. The Gibbs-Donnan equilibrium is a major controlling factor, especially because the hemoglobin molecule carries a large negative electric charge; and the increased acidity of hemoglobin on oxygenation is essential for adequate discharge of CO2 in the lungs. The maintenance of essential equality of pressure inside and outside the red cell is linked with what appeared to Van Slyke and others as impermeability of the cell membrane to cations. This hypothesis was adequate to describe the phenomena at the time; but later research showed that what appeared to be an equilibrium was actually a steady state, maintained by expenditure of metabolic energy