Human red cell age, oxygen affinity and oxygen transport

The [2,3-DPG]/[Hb] ratio and the P50 were found to be lower in the 10% denser (old) than in the 10% lighter (young) red blood cell (RBC) fractions (0.57 +/- 0.13 vs 0.96 +/- 0.13 and 23.02 +/- 0.85 vs 27.47 +/- 1.05 Torr, respectively, mean +/- SD, P less than 0.0005 for both, n = 6). The RBC aging processes appear thus to affect the RBC oxygen affinity. However, the [2,3-DPG] changes do not fully explain the drop of not fully explain the drop of P50 as measured at constant [H+], [CO2] and [HbCO]. It is therefore postulated that an additional factor is involved in the regulation of the oxygen affinity in the ageing RBC. The RBC density in 59 normal individuals matched for age (infants, adult, and aged) and for sex was found to be younger in adult females than in all other groups (P less than 0.0005), including an age-matched group of pregnant women. Correspondingly, the [2,3-DPG]/[Hb] ratio and the P50 are higher in adult females than in adult males (0.92 +/- 0.10 vs 0.82 +/- 0.09, P less than 0.009, and 29.03 +/- 1.07 vs 27.72 +/- 0.82 Torr, P less than 0.002, respectively). These data are evaluated in terms of the efficiency of the oxygen transport calculating the circulatory load required to transport a given amount of oxygen to the tissues. The results indicate that the lower oxygen affinity (due to the younger RBC population) in adult females partially compensates for their lower [Hb].