Base binding in erythrocytes

Abstract

THE inorganic cation content of erythrocytes is greater than the content of inorganic anion and most writers have assumed that the excess is combined with haemoglobin. This is the view of Henderson [1928], who, however, points out that cell base is sometimes in excess of HCO3-+Cl-+ Hb-. He considers this excess of base to be negligible in normals and due to the presence of small quantities of acids "not accounted for in the balance sheet." These acids he calls HX, and X-= B+-Cl--HCO3 -Hb-. Henderson calculates Hb-from Van Slyke's data for horse blood [Van Slyke et al. 1923]. Henderson, however, was working with human blood and as the buffering power of human haemoglobin is much less than that of horse haemoglobin it follows that Henderson's value for Hb-were too high and his figures for X-too low. In a recent paper, Maizels [1936] using Adair's data [1925] for the buffering power of oxyhaemoglobin came to the conclusion that in normal human cells the amount of base combined with HX, though small, was not negligible, and that in the erythrocytes of the microcytic anaemias the value of X-might rival that of Hb-itself. But the figures quoted were only approximate and suffered from the defect of being based on several assumptions: firstly, the value of cell bicarbonate was derived by calculation from plasma bicarbonate; secondly, the presence of other cell anions like phosphate was neglected; and thirdly, as cell pH was not known, the amount of base actually bound by haemoglobin could not be determined. It was there- fore necessary to assign certain limiting values to cell pH and in this way the value of X-was derived.