Oxidation of hemoglobin F is associated with the aging process of neonatal red blood cells

Abstract

Previously, we reported that in cord blood there is a population of very dense, surface area-depleted red blood cells (RBC). We hypothesized that oxidative damage might account for the generation of this cell population because Hb F is known to be mildly unstable in vitro. Accordingly, we examined density-separated subpopulations of neonatal red cells searching for evidence of oxidant injury to Hb in vivo. Cord or adult RBC were separated into populations of varying density and an increased amount of membrane-associated globin was found in the densest fraction of cord RBC. Solubilized ghosts from each fraction were analyzed by thiol-disulfide exchange chromatography for the presence of oxidized Hb and spectrophotometrically for the presence of membrane-bound hemichrome. About four times more oxidized Hb was found in unseparated cord RBC than in adult RBC. This difference was most evident in the densest 10-15% RBC subfractions. Membrane-bound hemichrome levels in cord cells were twice those found in adult cells. We found that in cord membrane skeletons there was 2.5 to 9 times as much globin in the dense fraction as compared to the light fraction. Membrane skeletons from dense and light adult RBC differed little from one another. We postulate that membrane (and perhaps membrane skeleton)-associated oxidized Hb is a marker for more generalized oxidative damage, which may create the population of unusually dense cells found in cord blood and ultimately shorten their life span.