Determinant factors for an apparent increase in oxygen affinity of senescent human erythrocytes

In the present work we have revaluated the old question of whether senescent human erythrocytes can handle oxygen delivery efficiently, by studying some factors determining haemoglobin-oxygen affinity of in vivo aged cells. Erythrocytes were separated according to their age using a novel approach for density gradient fractionation. The 5-10% least dense (young) and the heaviest (old) red cell fractions were separated by strict percoll density gradients under conditions inducing minimal cell stress, thus avoiding formation of aggregates. Aged cells showed a decreased content of organic phosphate compounds and additionally, an internal pH of about 0.2 pH units more alkaline than the younger cells. These results lend indirect experimental support for both an apparent increase in haemoglobin-oxygen affinity and a deficient oxygen release of in vivo aged human erythrocytes.