The relationship between the blood oxygen transport and the human red cell aging process

We have studied the relationship between the in vivo aging process of the human red cell (RBC) and its main function, the transport of O2 from the lungs to the tissues. This study included several approaches. First, we observed that the affinity for O2 in young RBCs was lower than in old RBCs (p less than 0.0005) due to different intracellular concentration of 2,3-diphosphoglycerate, main effector of hemoglobin. Second, we explored whether there are some subgroups of the healthy human population with altered RBC age distribution: females in the age range 25-35 exhibited significantly younger RBCs (p less than 0.0005) and lower RBC-O2 affinity (p less than 0.01) than other groups. Correspondingly, the RBC-O2 affinity in female blood was significantly lower (p less than 0.002) than in male blood. Third, we correlated by two independent methods the lowered RBC-O2 affinity to a more efficient O2 delivery to the tissues by two independent methods: 1) calculating the size of the cardiac output increase required to sustain the tissue oxygenation after an increase of the RBC affinity for O2; and 2) monitoring the enhanced cardiac function in isolated rat hearts perfused with RBCs at low O2 affinity. Finally, comparing some hematologic findings relevant for the O2 transport in two healthy populations with different RBC age distributions, such as age-matched females and males, it appeared that the low RBC-O2 affinity in females is an adaptive response to their lower [Hb].(