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 O2in young RBCs was lower than in old RBCs (p<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 <0.0005) and lower RBC-O2 affinity (p<0.01) than other groups. Correspondingly, the RBC-O2 affinity in female blood was significantly lower (p <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]. All these approaches agreed in indicating that the lowered RBC-O2 affinity, and by reflect the younger RBC average age, appears associated to more favourable conditions of tissue oxygenation. We conclude that the human RBC aging process is not only a suitable model to study the cellular and tissutal aging mechanisms, but may also have a considerable influence on some physiological and pathological patterns in humans.
KeywordsPolycythemia Vera Hereditary Spherocytosis Coronary Pressure Inositol Hexaphosphate Cardiac Output Increase
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