Velocity of O2 uptake by human red blood cells

Abstract

We have determined the over-all association rate constant, k'_c, for the uptake of oxygen by normal human erythrocytes from 0% to 97% initial hemoglobin saturation at pH 7.4 and 37óC. With a modified Hartridge-Roughton rapid-reaction apparatus, we used a small oxygen electrode to follow the oxygen uptake process rather than using the usual photocolorimetric analytical methods. The value of k'c averages 164 mm^-1 sec.^-1 at 0% initial saturation, rises slowly to over 300 at 50%, and then climbs rapidly to over 1500 at 95%. The theoretical explanation for the increase in k-_c with rising initial oxyhemoglobin saturation is based on the increasing prominence of the fourth chemical association rate constant, k-₄, in the intermediate compound theory of Adair. It is known that k-₄ is several times larger than any of the other three k–_s. Submitted on December 19, 1960