Chloride and Hydrogen Ion Distribution between Human Red Cells and Plasma

Abstract Distribution of Cl ‐ and H + between human red cells and plasma has been studied after variations of plasma pH (induced both by changing pCO 2 and changing bicarbonate concentration). The distribution ratio of chloride Cl ‐ cell /Cl ‐ plasma = r(Cl ‐ ), and of hydrogen ions H + plasma /H + cell = r[H + ], showed the following relations to plasma pH: r(Cl ‐ ) = 3.319—(0.359 pH plasma ) r[H + ] = 3.094—(0.335 pH plasma ) The conception that the distribution of Cl ‐ and H + is a Donnan distribution, is supported by the distribution of Cl ‐ and H + found after addition of an impermeant, negatively charged ion (citrate) to the extracellular phase. The normally negative potential difference between cells and plasma may be inverted in the presence of citrate. The effects on ion distribution seen, when normal cells are suspended in isotonic sucrose or glucose, can be explained as being caused by diffusion potentials, which arise because of the much higher permeability of the red cell membrane towards anions than towards cations. Calculation of the water shift to be expected as the osmotic consequence of the redistribution of diffusible anions between cells and plasma (—ΔH 2 O/ΔpH: 423g H 2 O/kg RBC solids) was found to agree with the experimentally determined value of 404g H 2 O/kg RBC solids.