Membrane-bound hemoglobin as a marker of oxidative injury in adult and neonatal red blood cells

A comparative study of the effect of hydrogen peroxide on adult and neonatal red blood cell (RBC) membrane protein composition has been carried out. The results indicate that (a) the native neonatal RBC membranes contain higher levels of membrane-bound hemoglobin (MBHb) than the adult RBC membranes. (b) The content of MBHb increases when RBCs are incubated with increasing concentrations of hydrogen peroxide (H2O2), more so in neonatal than in adult RBCs; however, neonatal RBC membrane proteins are less susceptible to H2O2 oxidation than adult ones. This could be attributed to the fact that Hb F, which is more susceptible to oxidation than Hb A, adds to the reduction potential of neonatal RBC (in which it is present in large amounts) and partially protects neonatal membrane proteins against oxidant stress compared to Hb A in adult RBC. (c) In both neonatal and adult RBCs, Spectrin 1 is relatively more susceptible to oxidant stress than spectrin 2, and spectrins in adult RBC are more labile for peroxidation than the spectrins in neonatal RBC. (d) Based on electrophoretic studies with and without reduction of membranes with mercaptoethanol, we have classified two types of MBHb: Type I is adsorbed to membrane by noncovalent interactions and Type II MBHb is chemically crosslinked to membrane components by disulfide bridges; the content of both these types increases when RBCs are incubated with increasing concentrations of H2O2. (e) Band 6 protein is present in higher amounts in neonatal than in adult RBC membranes. (f) Since the total content of MBHb increases linearly with the level of oxidant stress, we suggest that it could be used as a marker for oxygen radical-induced injury to tissues.