Red cell age effects on metabolism and oxygen affinity in humans.

Hemoglobin-oxygen-binding characteristics and essential influencing factors were investigated in human erythrocytes of different age separated by density gradient centrifugation. The most important age-dependent changes of the cell milieu are losses of K+, organic phosphates and water; the latter also leads to an increased concentration of negative charges on Hb. This augments the Donnan effect, which is only partly compensated for by a decrease of DPG-. The oxygen dissociation curve of the oldest fraction (P50 23.4 mm Hg) is shifted to the left compared to young cells (P50 29.2 mm Hg), and Hills 'n' is decreased (old cells 2.31, young cells 2.74). The Bohr effect for CO2 increases in the old population (BCCO2 at 50% SO2 -0.63 and -0.24 for old and young erythrocytes, respectively). This effect is less pronounced for the Bohr coefficients for lactic acid (delta BCLac 0.09). Most cell age-dependent alterations of Hb-O2-binding (including BCCO2) are explainable by opposite alterations of [Hb] and [DPG], causing the change of the ratio [DPG]/[Hb] from 1.3 to 0.7 during the aging process of the erythrocytes. Minor effects may result from aging of the Hb-molecule itself.